(Another shameless cross-posting from I Cite.)
Lots of different kinds of remarks don't travel; they don't circulate seamlessly from one context to another. Instead, their travels are stained with a kind of remnant or remainder. It may well be that this stain or remainder is central to their use; awareness of the stain, an irrational nugget, marks one as an appropriate user of the term. Often, becoming aware is difficult, painful; perhaps that it why it marks membership and appropriate use.
Several years ago my father gave Paul a 'personal groomer' for Christmas (read nosehair clipper, sideburn trimmer, multi-purpose hair removal apparatus for men). Because this was so traumatic, I frequently mentioned it, making fun of the gift. Yet, I was furious when I heard Paul and his sister joking about the groomer. They were making fun of my father, my family, and, by extension, me.