The story
- Old English · inherited fromopenears
- Middle English · inherited fromopen-ers
- English todayopen-arse
From Middle English open-ers, from Old English openears, corresponding to open + arse, ‘with allusion to the large cavity at the end of the fruit between the persistent calyx lobes’ – OED3.
First known use, by meaning
- from 10th c. The medlar fruit.
Etymology from Wiktionary, CC BY-SA 4.0.