Coachfellow is a compound of coach + fellow, denoting a horse harnessed beside another to draw the same coach; used figuratively for a partner or yokefellow. Morphologically, coachfellow is transparent: it is a compound of coach + fellow, denoting a horse harnessed beside another to draw the same coach. Used as a noun, coachfellow now means "a horse harnessed alongside another to the same coach; a yokefellow", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as coach and fellow. The modern word remains analyzable through its parts, which makes the semantic connection unusually direct.