ETYMOLOGY
from open + tail (posterior extremity)
EXAMPLE
“…Kate still exclaimes against great Medlers,
A busie-body hardly she abides,
Yet she’s well pleas’d with all Bum-fiddlers,
And hir owne Body stirring still besides:
I muse her stomacke now so much should faile,
To loath a Medlar, being an Open-taile…”
From: The Scourge of Folly,
By John Davies, 1611
Lexicophilia 