The word helpmate means a helpful companion or partner, especially one’s husband or wife.

This noun was originally helpmeet, about which the New English Dictionary (i.e. the Oxford English Dictionary – 1901 edition) explained the following:

A compound absurdly formed by taking the two words help meet in Genesis, ii, 18, 20 (‘an help meet for him’, i.e. a help suitable for him), as one word.

This biblical phrase appeared in the King James Version (1611); the Book of Genesis, 2:18-20, is:

18 And the Lord God said, It is not good that the man should bee alone: I will make him an helpe meet for him. 19 And out of the ground the Lord God formed euery beast of the field, and euery foule of the aire, and brought them vnto Adam, to see what hee would call them: and whatsoeuer Adam called euery liuing creature, that was the name thereof. 20 And Adam gaue names to all cattell, and to the foule of the aire, and to euery beast of the field: but for Adam there was not found an helpe meet for him.

Therefore:

21 And the Lord God caused a deepe sleepe to fall vpon Adam, and hee slept: and hee tooke one of his ribs, and closed vp the flesh in stead thereof. 22 and the rib which the Lord God had taken from man, made hee a woman, and brought her vnto the man.

In an help meet for him, meet is an archaic adjective meaning suitable, proper, and the Scripture phrase means a suitable helper for him.

But already in the 17th century, the phrase is found with the two words improperly hyphenated. This is first attested in Marriage a-la-mode (1673), a comedy by the English author John Dryden (1631-1700):

Well, if ever woman was a help-meet for man, my Spouse is so.

This led the way to the use of help-meet, helpmeet, as an autonomous noun, that is, not followed by for and a complement such as him or man. It is first recorded in The Entertainer of 12th February 1718. An article about polygamy contains the following:

At Athens Euripides had two Wives together […]. Socrates had the like Number of Helpmeets. And Athenæus concludes it was no Scandal in those Times.

In Religious Courtship: being Historical Discourses, on the Necessity of Marrying Religious Husbands and Wives only. As also Of Husbands and Wives being of the same Opinions in Religion with one another (1722), the English novelist and journalist Daniel Defoe (1660-1731) wrote:

I do not say you cannot go to Heaven without your Husband; or you cannot be religious without your Husband, but I do say you cannot go comfortably thro’ the Journey thither without him, or he without you: A Woman is to be a Helpmeet, and a Man is to be the same.

Probably under the influence of the more familiar word mate, the variant helpmate came into use during the same period. It is first attested in Athenæ Britannicæ: Or, A Critical History of the Oxford and Cambridge Writers and Writings (1716), by the Welsh bibliographer Myles Davies (1662-1719?):

The Monks and Cardinals of H. 8th’s [= Henry VIII’s] days had not forgot the Art of forging Manuscripts of far more Ancient Date, more Difficult Character and Resemblance than those Manuscripts can pretend to be; neither were the Jesuits so young then but that they could be notable Helpmates  to the Monks in that kind of Forgery.

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Had the King James Version of the Book of Genesis been different, the words helpmeet and a fortiori helpmate would not have existed. For instance, in the Early Version (around 1382) of the Wycliffe Bible, the Book of Genesis, 2:18-20, is:

18 The Lord God forsothe seide, It is not good man to be alone; make we to hym help like hym. 19 Fourmed thanne of the moist erthe alle thingis of the erthe hauynge soule, and al volatile of heuene, the Lord God brouȝte hem to Adam, that he shulde se what he shulde clepe hem; al thing forsothe of soule lyuynge that Adam clepid, that is the name of it. 20 And Adam clepide alle thingis hauynge soule, and al volatile of heuene, and alle beestis of the erthe, bi her names. To Adam forsothe was not foundun an helper like hym.

And, in the Coverdale Bible (1535), the expression is “an helpe, to beare him cōpany”.