'replenish' originates from Old French, specifically the word 'replenir', where the prefix 're-' meant 'again' and the root ultimately comes from Latin 'plēnō'/'plēnus' meaning 'full'.

'replenish' changed from Old French 'replenir' into Middle English as 'replenis(h/e)' and eventually became the modern English word 'replenish'.

Initially, it meant 'to fill again' (to make full again); over time this meaning was retained and is now expressed as 'to refill, restore, or supply again'.