handfast
verb
[ ˈhan(d)fɑːst ]
• engage (someone) to be married.
• "she was handfasted to my older brother Lewis"
handfast
noun
• an engagement or marriage contract.
• "the only thing that can undo a handfast is a lack of love"
Origin:
late Old English: from Old Norse handfesta ‘strike a bargain by joining hands’.
