'illiberal' originates from English, specifically formed by the negative prefix 'il-' (a variant of Latin 'in-') attached to 'liberal', where 'liberal' ultimately comes from Latin 'liberalis' and the root 'liber' meant 'free'.

'illiberal' developed in Modern English by prefixing 'il-' to the existing adjective 'liberal' (which came into English via Old French and Latin 'liberalis'), creating the modern word 'illiberal'.

Originally, 'liberal' meant 'generous' or 'relating to freedom'; the formation 'illiberal' initially conveyed 'not generous' or 'not free-minded' and has come to be used chiefly for opposition to political or civil freedoms in modern usage.