armhole

noun

Etymology: From Middle English arme hole, armehole, arm hole, arm-hole, armhole, arm-hool(e), armole, harmehole; equivalent to arm + hole.

1. A human armpit.

   “An aposteme gendred in þe purgynge places, þat is to say, of þe brayne vnder þe eres, of þe herte vnder þe arme holes, of þe lyuer in the schares.”

   “Put these ragges and cloutes vnder thine arme holes.”

2. Similar structures in other animals.
3. A hole for an arm in a piece of clothing.

   “He... violently pull'd off her Riding-Hood, and tore it at the Arm Holes in pulling it off.”