As far as I know, it's entirely facetious &/or meant in a wry manner/tone.
The people I'VE heard use it (all ladies) are using it with the underlying meaning of 'designated' being "they're-'designated'-meaning- they're-only-here-at-MY-pleasure-and-they-BETTER-behave-if-they-know-what's-good-for-'em-or-they'll-get-their-sorry-asses-REPLACED."
