I get the feeling this is going to run and run. I have a large.....collection of ballads that use sexual euphemisms and I'll have a look through but nothing immediately springs to mind. Most of the ballads are from earlier centuries. Intriguing!

A large section of the ballads include soldier/battle/weapon euphemisms so I'll start with these.

'sexual act performed illicitly' should narrow it down. There may be something hidden in Brophy and Partridge's songbooks.