@Merry Andrew,
Different strokes for different folks. English speakers tend to think the Latin-based words are more complicated, while those coming from experience with other Romance languages may find them much more natural and their more colloquial equivalents more difficult.
For example, "masticate" is the normal every day way to say "chew" in many languages. Autodidact is the same for me, that's just a literal translation of the easiest way to say it in other languages that I speak. Plus it has variations that don't work as well with "self taught".
In any case, I was pretty sure that the original poster was not asking for "self taught" and was pretty sure this is the term the user was seeking, I agree with the notion that it's pointless to opt for sesquipedalian* vocabulary just to try to impress people, mainly because it doesn't do that very well and tends to make them defensive, but at the same time I think most people have a silly defensive reflex when they encounter words they don't know.
The words aren't ever exactly the same, they have different textures. Calling a woman "callipygian" is just not at all the same thing as saying she has a "nice ass". I wish people would strive to elevate their vocabularies instead of trying to bring that of others down to their level (when I was younger I had to make a conscious effort to be more colloquial just to fit in). I hate the guy who sounds like he just found a thesaurus as much as the next guy, with big words shoe horned in awkwardly (and often incorrectly) where smaller words would do, but the derision of extensive vocabulary is more than just that. It's sometimes an extension of anti-intellectualism that seeks to mock those who know what you don't.
[/rant]
* yes, I could have used "big word" vocabulary, or "wordy" vocabulary, but that is not what I wanted to say. There's a perfectly good word for
exactly what I wanted to say.