'ascella' originates from Latin, specifically the word 'ascella', a diminutive form related to 'axilla', where 'axilla' meant 'armpit'.

'ascella' passed from Classical Latin into Medieval/New Latin and was adopted into English via medical (New) Latin as a technical anatomical term.

Initially it meant 'little armpit' (a diminutive sense), but over time it has been used in English to denote the 'armpit' or 'underarm' in anatomical contexts.