'aplenty' originates from Middle English, specifically formed from the prefix 'a-' plus the word 'plenty', where 'a-' originally meant 'on/in' and 'plenty' meant 'abundance'.

'aplenty' developed in Middle English from 'a-' + 'plenty'; 'plenty' itself came into English from Old French 'plente', which ultimately derives from Latin 'plenus' meaning 'full'.

Initially, it meant 'in abundance' (essentially the same sense as 'plenty'), and over time it has retained that core meaning of 'in great quantity'.