break-vow

noun1

1. •
   (disapproving, no longer used) An untrustworthy person; someone who habitually breaks vows and promises.

   • With that same purpose-changer, that sly devil, / That broker, that still breaks the pate of faith, / That daily break-vow, he that wins of all, / Of kings, of beggars, old men, young men, maids, — 1596