What is the family moto for the surname McKenna?

Prudentia et Honor. In Latin. Ignorantly believed at the time (late Middle Ages) to mean "Prudence and Honor". The term "honor" actually in correct Latin coming from the Word "hones" as in "cursus honorem". This phrase referred to the Roman "course of office"--ie quaestor, aedile, praetor, consul. As the achievement of the "offices" in the old Roman Republic over time morphed into the "honor" (in Latin "virtutes") of the "office". So honor actually means high office.