Caucasian is a term for a race. I think the name came from the Caucus mountain region of Europe, but I am not sure. Negroid is another name for a race. I think it came from the Spanish term "negra" which means black in Spanish. I don't know who made up the race names or when, but it was a long time ago. Some have become offensive through slang usage and use as slurrs. I will call a person whatever he or she wants, as some prefer African American, some prefer black. A few older folks I know still prefer Negro, or an old local pronunciation Negra, though spoken with respect that they deserve.
