Covenant of Redemption

The covenant of redemption is typically described as a covenant between the Father and the Son rather than as a covenant between all three members of the Godhead. This is because the Bible presents the Son as the Redeemer, not the Holy Spirit, and it presents the Father as the one who permits, commands and accepts the Son's sacrifice. The Holy Spirit is critically important to the salvation process, but the condition of redemption was to be fulfilled by the Son in obligation to the Father, and the Father was to reward the Son's obedience. This is the essence of the covenant of redemption: a condition laid on the Redeemer, and a reward promised to the Redeemer upon fulfillment of the condition. Biblical texts supporting this doctrine are quite extensive, but for a sampling of texts and proofs see my article Biblical Soteriology: Limited Atonement, part 12.

I'm afraid I'm not aware of when the term "covenant of redemption" first came into play. But the concept has been around much longer than the term. In fact, I can't think of any old, mainstream system of theology that would deny its basic ideas (though some newer systems do), although the specific terms of that covenant are disputed. Certainly the idea is present in Calvin (e.g. Institutes 2.12.4).

As in Calvin, I suspect that in very old systematic treatments the idea would be addressed under the heading of the purpose of the incarnation. One work that comes to mind is Anselm's "Why God Became Man" (late 11th century). Anselm certainly does not lay out the Reformed doctrine of the covenant of redemption. But he does indicate that the Son of God came to earth with the express purpose of redeeming mankind at the will of the Father and by satisfying God's Law, and he assumes that the Father assured the Son of success.