old wives' tales

An old wives' tale is a type of urban legend, similar to a proverb, which is generally passed down by old wives to a younger generation. Such "tales" usually consist of a superstition, folklore or unverified claims with exaggerated or untrue details. Today old wives' tales are still common among children in school playgrounds. Old wives' tales often concern puberty, pregnancy and nutrition.
Some examples of old wives' tales include:

• Ice cream leads to nightmares.
• It's bad luck to give a pair of gloves to a friend unless you receive something in exchange.
• Toes pointed up signify low blood sugar.
• High heart rates lead to female fetuses.
• If you step on a crack you'll break your mother's back/step on a line and break your mother's spine.
• Breaking a mirror will earn a person seven years of bad luck.
• Don't swallow gum or it will stay in your stomach for seven years.
• Various other stories, all resulting in "seven years" of something.
• It's bad luck to open an umbrella indoors.
• Making silly faces when the wind direction changes will make the silly face permanent

Citation:http://en.wikipedia.org/wiki/Old_wives%27_tale