I have seen a lot of people totally misusing this word.
the term Caucasian actually stems from a scientific theory...long since proven false...that white people originated from the caucus mountains...now in the region of the country of Georgia.
it referred to all people who were considered 'white' at the time...which included arabs and upper caste indians.
white people actually originated in europe. We know this now. Yes they did have invaders who expanded from ukraine to the south south around 4000 BC...and from ukraine to europe around 3500 BC, which had massive impact on eruopean genetics (for example the gene for blonde hair)
if you reduced the number of races on earth to 4 then yes, arabs and europeans would be in the same racial category.
but modern genetic science has found no use for such a category.
in scholarly genetic parlance of the modern era, the word 'Caucasian' does not refer to all white people, but simply the specific people around the country of georgia....who on a PCA graph are actually overlapping with the turks.
stalin was a caucasian. hitler was not.