'imbecile' originates from Latin, specifically the word 'imbecillus', where 'in-' (variant 'im-') meant 'not' and 'bacillum' (diminutive of 'baculum') meant 'a little staff' or 'support'.

'imbecillus' (Latin) passed into Old French as 'imbecile' and then into English (Middle English/early modern English) as 'imbecile', keeping the form and sense.

Initially it meant 'weak' or 'feeble' (physically or mentally) in Latin, then shifted toward 'weak-minded' and later became a common insult meaning 'stupid person'; it was also used as an early clinical classification for intellectual disability (now obsolete and offensive).