Doesn’t ring a bell, sorry… I know that ‘lie/falsehood’ in Latin is ‘Mendacem’ – ‘Fides’ = honesty, ‘Nulla fides’ = no honesty, ‘Veritas’ = truth… try some google-fu?

“Mendacem memorem esse oportet”

It is fitting that a liar should be a man of good memory

“Mendacium semper in multiloquio”

There is always a lie in too much talk

“Verum est, quod pro salute fit, mendacium”

A lie told to save yourself is true

“Fama crescit eundo”

Rumors grow through circulation

“Homines quod volunt credunt”

Men believe what they want to

“Mala malus mala mala dat”

A bad apple tree gives bad apples (Evil begets evil)

“Mundus vult decipi, ergo decipiatur”

The world desires to be deceived; therefore it is