helpmeet (n.)

Old English help (m.), helpe (f.) "assistance, succor," from Proto-Germanic *helpo (source also of Old Norse hjalp, Swedish hjälp, Old Frisian helpe, Dutch hulp, Old High German helfa, German Hilfe), from the source of help (v.).

The use of help as euphemism for "servant" is American English, 1640s (originally in New England). Bartlett (1848) describes it as "The common name in New England for servants, and for the operatives in a cotton or woollen factory." Most early 19c. English writers travelling in America seem to have taken a turn at explaining this to the home folks.  

A domestic servant of American birth, and without negro blood in his or her veins ... is not a servant, but a 'help.' 'Help wanted,' is the common heading of advertisements in the North, when servants are required. [Chas. Mackay, "Life and Liberty in America," 1859].

But help also meant "assistant, helper, supporter" in Middle English (c. 1200).

"companion," 1715, altered from helpmeet.

c. 1300, mēte, "having the right shape or size," from Old English gemæte, Anglian *gemete, "suitable, having the same dimensions," from Proto-Germanic *ga-mætijaz (source also of Old Norse mætr, Old High German gimagi, German gemäß "suitable"), from collective prefix *ga- + PIE root *med- "take appropriate measures." The formation is the same as that of commensurate. Meaning "proper, appropriate" is from early 14c.; that of "fit (to do something)" is from late 14c.

The mountain sheep are sweeter,

But the valley sheep are fatter;

We therefore deem'd it meeter

To carry off the latter.

[Thomas Love Peacock, from "The War-song of Dinas Vawr"]