"troussage" is an old-style french word euphemizing a sexual relation between a man and his female servant (a maid for example). Does it exist in English ?

 

Troussage is not an English word to my knowledge.

Within those classes that employ maids, there may be equivalent terms.
As I myself do not belong to these, I do not know.

 

i do not belong to it either ! someone has a clue ? like an 18th C literature scholar who would wander around this forum ?

 

"To tumble a chambermaid" is probably a good analogue. It's not a phrase that exists in modern usage, but you still see it in period fiction.

 

Please see this thread:
trousser les soubrettes
The two threads discuss the same idea.

There is heightened in interest in other expressions at the moment. You may also find this thread useful:
droit de cuissage