To be pissed off my half cut BIL taught my 3 year old son to call me a nickname?

[LadyOfWaffle]

Went to BIL/SILs on Saturday night and after finally returning from the pub to see us (wasn't drunk, just merry) he told my son (3) to call DH by a stupid nickname that he used to be called. His cousin started it, and even her little girls greet him with it in a smart tone. Then he told him to call me "mummy (nickname)", and even went as far to get him to call our baby son "baby (nickname)". I laughed it off, and told him I didn't care because it wasn't a real word but googling shows exactly what it is, and while not rude or anything I don't want to be called it! What can I do, because this will run and run now - DS called me it this evening so he obviously remembered it.

Hmmm, my DH taught my DD to call her uncle (my DH's brother) Fat-head, which is the nickname that all 3 brothers have for him. She remembered it wrong though and called him Head-fat by mistake. Which has stuck. I have to say it does make me chuckle when she talks about Uncle Head-fat. I suppose the difference here though is that this is a current nickname that he is called by all of his brothers so I don't think he's too offended.

On the flipside my DD's other uncle (another of DH's brothers) calls DD Spud Face and she gets really cross with him and tells him off.

In this family (well the brothers at least) nicknames are obligatory and i'd almost be offended not to have one.