SIL can be both son in law and sister in law.... confused yet? Acronyms are annoying. Sometimes I feel like people throw them around as if to say, "I know what it means and don't care if you don't"!
I do use the sewing acronyms, mostly just the common ones everyone knows. HSTs are half-square triangles, FMQ is free motion quilting. Those are two that I do use.