> valid and current, but not equally so.

That would be better phrased as "valid and often used."

"Not current" implies "on the way out," but broader/narrower sense relationships, like other kinds, can last for a very long time.

U.S. (and possibly U.K.?) example:

"Guy" mostly means male person. But it also applies to a group of made up of either or both sexes: "you guys" (often used by young women to young women, as well as by anybody to a mixed group).

All these usages are equally valid and current, despite the theoretical inconsistencies - which have been made much of by academic feminists.

As for "carnal," its unique known record, in the ballad, suggests that it was a rare, regional term that is now obsolete, except as it appears in the song.

Had they found another example, the Oxford editors would have included it. Nor is there another in the multi-volume "English Dialect Dictionary." Or anywhere, so far as I can tell.

Not even Oxford is certain that it meant "crow," but it's a reasonable guess.