'Sailor' was respelled from 'sailer' to separate the person from the ship — a rare spelling fix.
A person whose job involves navigating or working on a ship or boat; a member of a ship's crew.
From Middle English 'sailer' (later respelled 'sailor' by analogy with '-or' agent nouns), from 'sail' + '-er.' The root word 'sail' comes from Old English 'segel,' from Proto-Germanic *seglą, of uncertain deeper origin — possibly from PIE *sek- (to cut), referring to a cut or sewn piece of cloth. An alternative and less certain etymology connects it to Latin 'sagulum' (military cloak), though this may be a parallel formation