The word 'sup' has a direct lineage from Old English 'sūpan', meaning "to sip, drink, taste." It shares a common Proto-Germanic ancestor (sūpaną) with related words in other Germanic languages, such as Old Saxon 'sūpan' and Old High German 'sūfan'. This root is thought to be onomatopoeic in origin, imitating the sound of sipping or drinking. Over time, its meaning broadened from simply drinking to include the consumption of food, particularly in the context of the evening meal ('supper'), which is etymologically "the meal at which one sups." The core sense of taking in small amounts, whether liquid or food, has persisted from its ancient roots to its modern, somewhat archaic or dialectal usage.

This word is a simplex form. It is a native English word of Germanic origin, functioning as both a verb and a noun.