"brawny, fleshy and solid," 1743, from beef (n.) in colloquial extended sense "human muscle" + -y (2). Related: Beefiness.
Entries linking to beefy
beef n.
c. 1300, "an ox, bull, or cow," also the flesh of one when killed, used as food, from Old French buef "ox; beef; ox hide" (11c., Modern French boeuf), from Latin bovem (nominative bos, genitive bovis) "ox, cow," from PIE root *gwou- "ox, bull, cow." The original plural in the animal sense was beeves.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.