Young people these days only use the word "slut" in dirty talk, such that calling someone a slut in polite company is now unacceptable. The sluts stole the word for themselves. Great job, sluts!
It went from a patriarchal normative, to being reclaimed. Are people down voting over the ambiguity of "polite"? Or because rediscovering the term "reclaimed" isn't really a shower thought?
Calling someone a derogatory term has never been acceptable in polite company. It doesn't really make sense.
Although the ultimate origin of the word slut is unknown, it first appeared in Middle English in 1402 as slutte (AHD), with the meaning of 'dirty, untidy, or slovenly woman'.