'armhole' originates from Modern English as a compound of 'arm' + 'hole'; 'arm' refers to the body limb (from Old English 'earm') and 'hole' meant 'an opening or hollow' (from Old English 'hol').

'arm' changed from Old English word 'earm' and 'hole' from Old English 'hol'; the compound 'armhole' developed in Modern English to denote the opening in a garment for the arm.

Initially it meant 'a hollow or opening for the arm' and over time it has retained this core meaning in reference to clothing openings.