Everywhere I looked agreed it is from Latin tiara, which was in turn a borrowing from Greek, but it's not clear if we can trace it back further. The OED describes it as being "of unknown origin" and Wiktionary likewise, but Etymonline suggests the Greek word is "of Oriental origin". Geoffrey Munn, quoted in Wikipedia, suggested the word is from Persian and was applied to the crown worn by Persian kings. It was indeed, but I'm not sure we can infer from this that the word was Persian.
My doubt arise from the fact that Munn also mentions diadems as being wrapped around said tiaras.
This is also true, but diadem is pure Greek; it has a Greek meaning, something like 'around binding'. The OED explains its etymology in this way, and describes it as "the regal fillet of Persian kings" (which I rather like) and states that Alexander the Great adopted it in the course of his conquests. So the headgear was indeed Oriental but the name used for it by Greek writers was a Greek one.
So we have no real evidence for "tiara" being of Persian origin that I can see; the Greek may have borrowed it from somewhere else, or it might have been pre-Greek, or it might have Greek etymology now lost to us.
So my quest for the origin of "tiara"only took me so far and I think the OED's conclusion that the Greek word τιάρα is of unknown origin is sound.
Tiaras and Diadems
When I came to this crossword clue —
— I wondered where "tiara" comes from.
Everywhere I looked agreed it is from Latin tiara, which was in turn a borrowing from Greek, but it's not clear if we can trace it back further. The OED describes it as being "of unknown origin" and Wiktionary likewise, but Etymonline suggests the Greek word is "of Oriental origin". Geoffrey Munn, quoted in Wikipedia, suggested the word is from Persian and was applied to the crown worn by Persian kings. It was indeed, but I'm not sure we can infer from this that the word was Persian.
My doubt arise from the fact that Munn also mentions diadems as being wrapped around said tiaras.
This is also true, but diadem is pure Greek; it has a Greek meaning, something like 'around binding'. The OED explains its etymology in this way, and describes it as "the regal fillet of Persian kings" (which I rather like) and states that Alexander the Great adopted it in the course of his conquests. So the headgear was indeed Oriental but the name used for it by Greek writers was a Greek one.
So we have no real evidence for "tiara" being of Persian origin that I can see; the Greek may have borrowed it from somewhere else, or it might have been pre-Greek, or it might have Greek etymology now lost to us.
So my quest for the origin of "tiara"only took me so far and I think the OED's conclusion that the Greek word τιάρα is of unknown origin is sound.