means To perceive an odor through the nose, or to give off such an odor — and by extension, to detect something amiss.

from From Middle English smellen, of obscure origin — one of those everyday words whose deep roots have gone quiet. It surfaces in English around the 12th century with no clear continental cousin; Old English seems to have preferred stincan (the ancestor of 'stink') and odor-words borrowed from Latin. Possibly related to a Low German or dialectal form meaning 'to smoulder' or 'glow,' as if scent were a kind of slow burning carried on the air — but this link is suggested, not proven. Honestly, where smell came from is itself a bit hard to sniff out.