Meaning – to get married
In Context – (1) After being engaged for years, Claude and Marie have finally decided to tie the knot next year. (2) Although John and Mary have lived together for the last 20 years, they have never tied the knot.
Origin – This idiom refers to an ancient Celtic tradition called handfasting. Couples were once tied at the wrist during the marriage ceremony and were only released when the marriage had been consummated.
Alternative Idiom (slang) – get hitched. Claude and Marie have finally decided to get hitched next year.