shibboleth

1 an attention-getting word or phrase used to publicize something (as a campaign or product) we knew that their claim of giving “the best deal in town” was just a shibboleth Synonyms banner, catchphrase, cry, slogan, tagline, watchwordRelated Words expression, idiom; catchword, cliché (also cliche); maxim, motto; battle cry, war cry

2 an idea or expression that has been used by many people there's a lot of truth in the shibboleth that if you give some people an inch, they'll take a mile Synonyms banality, bromide, chestnut, cliché (also cliche), groaner, homily, platitude, commonplace, trope, truismRelated Words conventional wisdom, party line, routine; inanity; generality, generalization, simplification; adage, proverb, saw, saying; old wives' tale, stereotypeNear Antonyms profundity