'Annamese' originates from English, specifically built from the place-name 'Annam' plus the suffix '-ese'; 'Annam' itself comes from the Chinese word 'Annan' (安南), where the characters meant 'pacified' ('an') and 'south' ('nan').

'Annamese' changed from the place-name 'Annam' (used in Chinese and later in European sources for parts of central/northern Vietnam) with the English adjectival/nationality-forming suffix '-ese', and eventually was used in English to refer to people or language of Annam; over time the modern term 'Vietnamese' replaced it.

Initially, it meant 'of or from Annam' (a specific historical region/administrative unit); over time its use declined and the modern, preferred term became 'Vietnamese', so 'Annamese' is now archaic and mostly historical.