McGrath:

'"skivvie" and "slavey" means the same thing'.

Indeed, and that's what's a bit odd about it -- why does one term replace the other, since there's virtually no difference in meaning?

"slavey" is the earlier recorded -- from about 1810+. "skivvy" is first recorded in 1902. Early 20thC, they seem to co-exist, and a lot of the citations read "skivvy or slavey". Then after mibee 1920, it's "skivvy" virtually universally.

"skivvy", as McGrath rightly points out, was the lowest of the low. In a five-servant Edwardian household, it might run [descending] (female)-- housekeeper cook skivvy; (male) -- butler, boots. Add in the lady's maid.

But that's upmarket. The norm I'd guess is for there to have been one female servant -- the slavey/skivvy.

A muddle ...

Snuffy:

fitbaw?

Robin