Santa Claus" has its origins in the figure of Saint Nicholas, as izzy says.
In his honour, children have always been given presents on 6 December since the 14th century.
In the figure of Saint Nicholas, two historical persons are merged. One is Nicholas of Myra: he lived in the third century and was the bishop of a town in what is now Turkey. The other historical person merged into the figure is Nicholas of Sion from the sixth century, who lived in a town near Myra. The legends about the lives of the two men interwove to form the figure of Saint Nicholas of Myra, who, according to the traditional stories, performed numerous miracles: He calmed a storm, brought the dead back to life and saved three young women from prostitution by throwing gold pieces through their father's window at night. This selfless act gave birth to the myth of the merciful helper and protector who, unrecognised, gave gifts to children in the night.
But then came Martin Luther, the reformer, who did not think much of the veneration of saints.
He propagated: away from the cult of individual persons, back to faith, to Jesus. The custom of St. Nicholas on 6 December still exists today (in the Netherlands it is Sinterklaas). But with the Reformation in the 16th century, the great gift-bringer was to become someone else. Around 1530, Luther established the "Holy Christ" as the gift-bringer, who had nothing to do with consecrated bishops. According to Luther's wishes, the gift-giving would no longer take place at the beginning of the month, but at Christmas.
In the end, the figure of Father Christmas is the amalgamation of those two. customs, increasingly detached from the Christ Child and the original Saint Nicholas in the course of the 19th century and becoming more and more secular.
In the search for the origins of the Christmas tree tradition, one finds less in the Bible and more in the Koran: Maryam - Arabic for Mary - is surprised by labour pains and leans against a tree. And there, under the shade of the (Christmas) tree, Isa - Arabic for Jesus - is born. The tree, however, was a palm tree.
The Christmas tree we are familiar with today probably has its origins in pagan tradition. At the time of the winter solstice, people brought so-called winter mai into their homes. These green branches were a sign of life, were supposed to drive away winter spirits and promised protection and fertility.
In the late Middle Ages, paganism was mixed with Christianity.
From the Middle Ages onwards, the church began to depict biblical scenes in order to teach the uneducated people. The story of Adam and Eve in paradise was popular. For the paradise story, of course, a 'paradise tree' was needed. This had to be evergreen - the fruit of knowledge, on the other hand, was initially a red apple.
So a coniferous tree was needed: the birth of the later Christmas tree.
The green tree with the apple was therefore not originally used to tell the Christmas story - but that of Adam and Eve and the serpent. In the course of time, the "tree of paradise" developed a connection to the Christmas story - and can therefore be regarded as the archetype of the Christmas tree that was later decorated with golden nuts, biscuits and baubles.
Incidentally, the first mention of a decorated Christmas tree is in connection with a bakers' guild in Freiburg in 1419.
From 1730, the trees were also decorated with candles for the first time.
At first, however, the Christmas trees were only found in the homes of Protestant families. The fir tree conquered living rooms across denominations during the wars of liberation against Napoleon at the beginning of the 19th century. At that time, the tree became a symbol of Germanness and was recognised as a part of Christmas, regardless of denomination.
Driven by the family ties of German noble families to the courts abroad, the Christmas tree gradually spread throughout Europe. Emigrants and especially German soldiers who fought in the American War of Independence also made it popular in the USA in the course of the 19th century. In 1891, a "Christmas Tree" stood in front of the White House in Washington for the first time.