handfast
A hold, grasp; custody, power of confining or keeping.
obsolete
The hand-fast to her lord. I have given him that
And the remembrancer of her to holdA contract, agreement, covenant; specifically betrothal, espousal.
obsolete
Where it comes from
From Middle English hondfast, past participle of Middle English hondfesten (“to betroth”), from Old Norse handfesta (“to strike a bargain, pledge”), itself from hönd (“hand”) + festa (“to fasten, fix, affirm”), perhaps from a Proto-Indo-European root *pHst-.
Adapted from the Wiktionary entry handfast (CC BY-SA 4.0).