'azlactone' originates from modern chemical English, specifically a combination of the prefix 'aza-' (used in chemical nomenclature to indicate replacement by nitrogen) and 'lactone' (from French 'lactone', ultimately from Latin 'lac' meaning 'milk').

'azlactone' was coined in 19th-century organic chemistry by joining the established chemical prefix 'aza-' with the term 'lactone' (the latter coming into chemistry from French 'lactone' derived via New Latin from Latin 'lac'). Over time the compound name became standardized to refer to 2-oxazolone-type intermediates (commonly appearing in the Erlenmeyer azlactone synthesis).

Initially, 'lactone' related etymologically to 'milk' but in chemical usage it came to mean a cyclic ester; 'azlactone' originally named a nitrogen-containing lactone-like ring system and has come to denote specifically oxazolone intermediates used in amino-acid chemistry.