'barrel-aged' is a Modern English compound formed from the noun 'barrel' + the past participle of the verb 'age' (i.e., 'aged').

'barrel' comes into English via Middle English 'baril' / 'barrel' from Old French 'baril', ultimately from Medieval Latin 'barriculum' (a small barrel). 'Age' comes from Old French 'aage' (modern French 'âge') from Latin 'aetas' meaning 'age' or 'lifetime'. The compound 'barrel-aged' developed in Modern English, gaining currency in the 20th century and becoming especially common in brewing and distilling contexts in the late 20th and early 21st centuries.

Initially, the elements referred simply to the container ('barrel') and the process of ageing; combined, they originally meant 'having been matured in a barrel' and this core meaning has remained stable while broadening to describe many products beyond spirits (e.g., beers, syrups, cheeses).