Archaic. a covenant or contract, esp. a betrothal, usually completed by a handclasp.
Origin: 1150–1200; ME (ptp.), earlier handfest < Scand; cf. ON handfestr, ptp. of handfesta to betroth with a joining of hands, equiv. to handhand+ festa to betroth, lit., make fast, fasten
hand·fast (hānd'fāst') n.
Archaic A handclasp used to signify a pledge, such as a contract or marriage.
[From Middle English hondfast, past participle of hondfesten, to betroth, from Old Norse handfesta, to strike a bargain, pledge : hönd, hand + festa, to fasten, fix, affirm; see past- in Indo-European roots.]