Brewer's: True-lovers' Knot
is the Danish trolovelses knort, “a betrothment bond,” not a compound of true and lover. Thus in the Icelandic Gospel the phrase, “a virgin espoused to a man,” is, er trulofad var cinum mannë.
Three times a true-love's knot I tie secure; Firm be the knot, firm may his love endure.
Gay's Pastorals: The Spell.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894