'angustifolius' originates from Latin, specifically from the combination of 'angustus' meaning 'narrow' and 'folium' meaning 'leaf', forming the adjectival compound 'angustifolius'.

'angustifolius' was formed in Classical/Medieval Latin as an adjectival compound from 'angustus' + 'folium' and has been adopted into Modern botanical Latin and scientific names as a species epithet (e.g. 'Lupinus angustifolius').

Initially it meant 'narrow-leaved' in Latin botanical usage, and this basic meaning has been retained in modern scientific nomenclature.