It’s still considered a four-letter word over here, not an obscure term at all, and you wouldn’t call a female colleague that word unless you wanted to lose your job. It’s pretty obvious why the character’s legacy name has been changed – no different to when that Power Core Combiners figure “Spastic” was renamed before release (in British terms that was like giving a Transformer character the name “******”). Call it critical research failure on behalf of whoever named Slag back in the ‘80s, but I don’t really blame American writers back in the pre-internet age for not being experts in British English.
I understand why both are changed, but I don't agree with "no different".
One of those words is still derogatory (and considered offensive by some) even in the meaning Hasbro intended, just far
less so than the British-specific meaning.
Incidentally, "
slag" (unrelated to the English word) actually means "hit" or "punch" in the Scandinavian languages, from the same etymology as the English "
slug" meaning the same thing.
Which makes me even more certain that the intended meaning of the name change to "Slug" is that, not the "bullet" meaning some insist on.