'Smell' may trace to 'to smoulder' — perceiving something like smoke. It replaced neutral 'stincan.'
The faculty of perceiving odours; a quality perceived by the olfactory organs; to perceive by inhaling through the nose.
From Middle English 'smellen' (to emit an odour, to perceive an odour), of uncertain origin. Possibly from Old English *smyllan or *smellan (unattested), perhaps related to Middle Low German and Middle Dutch 'smelen, smölen' (to smoulder, to burn slowly). If this connection is correct, the original sense was 'to smoulder' — smell was first perceived as something that smoulders or emanates, like smoke from a slow fire
Old English 'stincan' originally meant simply 'to smell' — with no negative connotation at all. It could describe flowers as easily as garbage. 'Smell' replaced it as the neutral word, and 'stink' was demoted to mean only 'to smell bad.' The same fate befell many neutral words: they become negative, and a