An archaic or dialect term, possibly meaning a courser (a horse) or a person who runs/rides, though its precise meaning is uncertain.
Possibly from courser (a swift horse or rider), with vowel shift reflecting dialectal variations. The etymology is obscure and may relate to Middle English 'cors' (course) or Old French 'coursier.'
Many dialect words like 'cooser' disappear not because they're forgotten but because entire ways of life vanish—when horse culture disappeared from daily life, so did words only horsemen needed.
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