the word 'supply' entered english in the late 14th century from the old french 'soupplier', meaning "to fill up, make full, complete." this old french term itself descended from the latin 'supplere', a compound of 'sub-' (meaning "up from below") and 'plere' (meaning "to fill"). the core logic is of filling something up from beneath, thereby making it complete. over time, the sense of "filling up" broadened into the more general modern meanings of providing what is needed to meet a requirement or the stock of what is provided.

the word is a simplex unit derived from latin. it cannot be meaningfully segmented into smaller morphemes using its modern english spelling without altering the form (e.g., 'sup' and 'ply' are not independent morphemes in this word).