The root word comes from Sanskrit and means "noble." As conquering tribes tended to see themselves as noble and their hapless victims as barbarian, i consider the creation of the neologism to have been reasonable. The 19th century was the glory era for linguistics, and the era in which linguistic investigation coupled with cultural investigation began to unlock the secrets of the relationships of peoples to one another. Archaeology only began to become a serious discipline in the late 19th century, but it has since been enlisted in the cause of the first "multi-disciplinary" study, that of the origins of peoples in pre-history. To give credit where it is due, archaeology has far more often than not tended to confirm the conclusions which linguists in the 19th century had reached. For example, linguistically, the Koreans and the Japanese are speakers of Altaic languages, which means that their nearest linguisitc cousins are the Turks, not the Chinese. (Even Chinese is an omnibus term, as it covers a multitude of cultures and languages.) Archaeology bears out a significant migration from the Altai mountains to the Korean peninsula in the appropriate time frame.
So, the term Aryan was originally a rather innnocent linguistic term which only vaguely supposed an aboriginal Aryan tribe from which the lnaguages described by that term derived. Modern linguistic research has cast doubt on whether the "Aryans" who invaded northern Indian in the mists of time were in fact a "root" culture and language. The modern term for the language group which includes the peoples of northern Indian who invaded thousands of years ago is Indo-Iranian. The term Indo-European is still in use, because there is a good deal of linguistic evidence for a common origin. However, there is no good reason to assume that the tribes who invaded northern India so long ago were the direct descendants of the "root" people from whom these languages derive.
So, from a linguistic point of view, no it would not be delusional, it would just be out of date. Contemporary linguistic theory no longer asserts that there was any reason to believe that the invaders of northern India were "ur-people" from which all of these languages derived. It wouldn't be delusional, just mistaken.
However, even among the woolier of the 19th century linguists, no one had ever attempted to assert that there were an indentifiable people who were the orriginal "Aryans." Modern archaeology has not found any such people. That's not to say that they won't be found, but the modern linguistic evidence is that the "Aryans" were not that people. The delusion creeps in when people start asserting that the Aryans did this, or the Aryans did that, or the Aryans were from here, or the Aryans were from there, and so forth.
There's an excellent Carnegie library in Columbus, Ohio, and about 20 years ago, i went through their history section looking for survey histories of European nations. This had two objects. One was to renew the outline history of Europe which i keep in my head. The other was to study the texts themselves, as 19th and early 20th century survey histories tell one a good deal about what people wanted to believe about themselves. In one of the survey histories of Sweden published in the late 1930s, the author asserted that Sweden was "obviously" the home of the original Aryans. (How they made it to the valley of the Indus River in a couple of years he did not choose to elucidate.)
An allegation that people from northwestern Europe could have reached the islands north of Japan several thousand years ago is not implausible. To suggest that they made it there from Karelia is stretching things a bit, though, as one would have to assume that they first sailed the Baltic and north along the coast of what is now Norway. Many scholars from northern Europe have long speculated that there was a circumpolar "culture," or at least circumpolar commerce in the primitive sense of commerce. It's not an unreasonable speculation, but, so far, it is only speculation. Also, the more sophisticated and better informed climatology of recent decades (since the mid-20th century) strong suggests that the Arctic Ocean was ice-free in summer for most of the period from 10,000 to 3,000 years ago, and at the height of that climatological period may have been ice-free year round.
It is, however, a bit much to suggest that people just shot out into the deep blue ocean to see what they would find. It is not unknown, but it is certainly not common. The people of Madagascar are descended from Australasians, who, apparently, sailed across the Indian Ocean (probably on the wings of the monsoon) about three thousand years ago. They have been significantly mixed with people from the mainland of Africa, but the language and the cultural antecedants are from what we would call Indonesia. (Indonesia itself was colonized by people from south "China" ["China," per se
, did not exist until the late third century BCE.], the Australasians who crossed to Formosa (Taiwan) and then to the Philippine islands, and finally to almost all of the islands of the China Sea, the Indian Ocean and the Pacific Ocean.
So, in effect, the Australasians constitute one a single example of people who were willing to set off into the unknown. There are serious problems in doing so. If you don't know to a certainty that you will find land within a certain period of time, you have the problems of food and water. You can get food from the sea, but you can't get "fresh" water. It is possible that having left south "China," the Austalasians had become sufficiently adroit to take the risk of sailing out several days to see what was out there. Finding floating vegetation, or seeing birds which were in their experience shore birds could tell them that land was not far off. By such a process, all of Macronesia and Micronesia ("Polynesia") could have been colonized. The one great venture was setting off across the Indian Ocean to make a landfall on Madagascar. It would not be an unreasonable assumption that some fishermen or explorers were blown west by the monsoon, found Madagascar, sailed back home after the monsoon, and convinced people to set out as colonizers when the next monsoon came around.
So, as far as i know (and i don't claim encyclopedic knowledge), the Australasians were the only people who have routinely set off into the unknown, assuming all of the attendant risks. Far more common has been that people will "coast," not sailing out of sight of land. That way, you have access to fresh water, and you can hunt and gather food along the way. If, as climatologists believe, the Arctic Ocean was, at least seasonally ice-free thousands of years ago, then it would not be implausible that people from northwest Europe made it as far east as Kamchatka, and then south to Sakhalin Island. (Just so you'll understand, i'm still in effect responding to Valtui's post.) However, this would still have some serious problems for the thesis. Someone coming from Karelia would still either have to sail the Baltic to what we call Norway, and then north around Scandanavia to the White Sea; or they'd have to hike north to the shores of the White Sea and build their boats. Furthermore, the Japanese consider the people who inhabit the northern Island of Hokkaido--the Ainu--to be primitive barbarians, from whom they are definitely not
descended. Finally, the linguistic evidence is against the entire proposition. The Japanese speak an Altaic language, akin to Korean and Turkish--they do not speak an Indo-European language.
There is much we can learn about the pre-historic period from language, culture and archaeology. None of those disciplines, as far as i am aware, support the silly notion that anyone has ever identified the original "Aryans," (other than the tribes who invaded northern India). Futher complicating the issue is the increasingly popular idea that there never was such an invasion of India, and that the Indo-Aryans in fact left India sometime between 4000 and 3500 years ago and invaded central Asia, giving rise to the Indo-European languages. That really throws a stick in the spokes of the Aryan wagon. There is even alleged to be genetic evidence for this thesis.
In the end, the only historical evidence we have of the appearance of so-called Aryans is the report about 3000 years ago by the Assyrians of the arrival of the Medes and the Farsi, the people whom western history would dub the Persians. All the rest is speculation. The speculation about language and culture is fairly well founded and has been refined over time. Genetics may some day provide better answers. Claims about "the Aryans did this" or the "Aryans did that" remain delusional, and are almost always to be associated with racist cults of "racial superiority" and "racial purity." What makes it hilarious is the appearance of Indo-Aryans in India today.
Do these boys look like the master race to you?