big-ass

The compound 'big-ass' is a modern American English slang formation. The first element, 'big', is a straightforward adjective of Germanic origin. The second element, 'ass', is a vulgar slang term for buttocks, derived from the Old English 'ears' (via 'arse'). In this construction, 'ass' functions not with its literal meaning but as an intensifying suffix, a common pattern in informal English (e.g., 'lame-ass', 'dumb-ass'). The compound's logic is one of hyperbolic emphasis, using a crude bodily reference to amplify the sense of size or significance, transforming a simple adjective into a more forceful and colloquial descriptor.

Structure: big (large) + ass (intensifier) big (Old English origin, meaning 'of great size or importance'); ass (American English slang, from 'arse', meaning 'buttocks', used as an intensifying suffix).