I don't know the name for this phenomenon, but I can think of one more example: "sanction" as a verb means to approve, while "sanction" as a noun is a ban.

As for the current meaning of "wicked," I suspect that's an extrapolation of the 1970s' "bad."

In the same vein, there are words that seem to be antonyms but are in fact synonyms, such as "flammable" and "inflammable."

Hope someone knows what these two groups of words are called.

linguaphile