I’m as aware as anyone of the high percentage of words that don’t have known etymologies (boy and dog, for instance), but every once in a while an example strikes me with particular force. Just now it was griot, in the words of the OED “A member of a class of travelling poets, musicians, and entertainers in North and West Africa, whose duties include the recitation of tribal and family histories; an oral folk-historian or village story-teller, a praise-singer.” I was aware that the Mande languages spoken in the area don’t use this word or anything like it (the Bambara word, for example, is jeli), but I was surprised to see the OED’s “uncertain ulterior etym.” Merriam-Webster simply says it’s from French. So I went to the Trésor de la langue française informatisé and found that it went back to 1637 (as guiriot) and that the etymology is, yes, uncertain: “peut-être issu, par l’intermédiaire d’un parler négro-port., du port. criado « domestique ».” Hmm. I don’t much like it, but I guess it’s possible. Why wouldn’t they have adopted a local word for such a characteristic local phenomenon, though?