'avuncular' originates from Latin, specifically the word 'avuncularis', where 'avunculus' meant 'maternal uncle' (a diminutive of 'avus').

'avuncular' changed from the Latin word 'avuncularis' (derived from 'avunculus') and was adopted into English from New Latin/Latin usage to form the modern English word 'avuncular'.

Initially it meant 'of or pertaining to an uncle', but over time it also came to mean 'kindly or benevolent in a way associated with an uncle' (an affectionate, advisory manner).