to be frank
/təbi fɹˈaŋk/
/təbi fɹˈæŋk/
Etymology
GermanicLatinOld FrenchEnglish
Built on the adjective 'frank', meaning open and honest, which came into English from Old French 'franc'. The Franks were a ruling Germanic people, so 'frank' first meant 'free', then later 'speaking freely without holding back'. The set phrase frames a coming remark as plain and unguarded.