I currently have an ulcer on my tongue.
The first time I ever mentioned I had an ulcer on my tongue my mother told me I must have told a lie. I was about four. There was a pretty fair chance that I had told a lie at some point, so I never mentioned it again.
Also, there's the furphy about not making a face in case the wind changes and your strange expression stays as a permanent look.
My mother also told me that writing on your skin gives you ringworms.
My mother's friend told me that earwigs got their name because they crawled into sleeper's ears at night. I spent years with my hand covering the ear not pressed into the pillow.
Does anyone else have any special insights from their mothers/aunts/fathers/uncles etc?