have a forked tongue

have a forked tongue

To make empty or false promises; to speak duplicitously or beguilingly. Likened to having the tongue of a serpent, a traditional symbol of deceit and dishonesty. That's the last time I lend Brian any money, that guy has a forked tongue! He learned quickly that having a forked tongue was an effective way of getting ahead in business.
See also: forked, have, tongue