|old wives' tale|
|a belief, usually superstitious or erroneous, passed on by word of mouth as a piece of traditional wisdom|
old wives' tale
A superstition, as in Toads cause warts? That's an old wives' tale. This expression was already known in ancient Greece, and a version in English was recorded in 1387. Despite invoking bigoted stereotypes of women and old people, it survives.