Douglas Harper's Etymology Dictionary
Wiktionary
well-hung
a. 1 (context informal vulgar English) Having a large penis. 2 (context of game meat English) Allowed to mature correctly.
Usage examples of "well-hung".
If the whitewash was all but gone from the stout wooden walls after the winter storms, the house was still in a tidy state of repair, the thatch tightly mended and the doors and shutters well-hung and snug fitting.
There's our well-hung Dominican and his young acolyte, Brother Christophe - a real treat, you see.