The compound 'throw-up' is a phrasal verb nominalization originating in the 18th century. The verb 'throw' carries its core sense of forceful propulsion or expulsion, while the particle 'up' indicates the direction of the expelled matter from the stomach. The vivid, almost violent imagery of the original morphemes provides a direct and euphemistic description of the physical act of vomiting. This construction follows a common pattern in English where a literal phrasal verb develops a specific, often informal, idiomatic meaning.

Structure: throw (to propel) + up (upward direction) 'throw' is from Old English 'þrāwan' (to twist, turn), of Germanic origin. 'up' is from Old English 'ūp', an adverb of direction, of Germanic origin.