'well-fed' originates from English, formed as a compound of the adverb 'well' and the past participle 'fed'. 'well' comes from Old English 'wel' meaning 'in a good or sufficient manner', and 'fed' is the past participle of 'feed', from Old English 'fēdan' meaning 'to supply with food'.

'feed' changed from Old English 'fēdan' to Middle English 'feden' and produced the past participle 'fed'; the compound 'well-fed' developed in Early Modern English as a straightforward combination of 'well' + 'fed' and has been used since around the 16th–17th century.

Initially it meant 'well supplied with food' and over time it has largely retained this meaning of being adequately or abundantly nourished.