My sisters and I have created our own language; I think every close family does it. We have phrases and expressions that we use all the time and which don't always have explanations that seem to fit their use. For example, "be careful of the icy patch" comes from our childhood (see previous post) and could be used as an ironic reference to an ex-boyfriend who has become rather sketchy, or it could be said while family members enter mom and dad's house, or it might be used on Christmas morning as a declaration of unity: (ie, as all the sisters raise mugs and declare laughingly, "be careful of the icy patch!")
This ridiculousness is what makes family... well, family. Dorky inside jokes and stupid memories that get replayed over and over (sometimes to the chagrin of brothers-in-love or soon-to-be brothers-in-love) over dinner and coffee and dessert and breakfast and at the movies and in the car and so on and so on.
The cool thing about husbands joining the ranks of the M girls is that the inside jokes get explained (even if they intrinsically do NOT make sense) and then, when you have the good taste that my sisters have, the husbands join in. Because they are pretty cool guys, when all is said and done. After all, any man who thinks that one of my little sisters is A Dandy Little Bundle for a Fella to Cuddle is all right by me.