'avourneen' originates from Irish (Gaeilge), specifically the vocative phrase 'a mhuirnín', where 'a' is the vocative particle (addressing someone) and 'mhuirnín' is the lenited form of 'muirnín' ('little beloved' or 'darling').

'avourneen' changed from the Irish vocative 'a mhuirnín' (used in direct address) through anglicization and phonetic rendering into Hiberno-English as 'avourneen' (and variant spellings such as 'avooreen' or 'avoroon').

Initially it meant 'O little beloved' (vocative expression in Irish), but over time it evolved into the English-language affectionate noun or form of address meaning 'darling'.