David is driving his ten year old granddaughter Rachel to school one morning when he accidentally hits his car's horn.
Rachel looks at him and asks, "Why did you toot your horn, Grandpa?"
"I didn't mean to do it, Rachel," David says. "I hit the horn by mistake."
"I knew it must have been a mistake, Grandpa," says Rachel, "because you didn't say 'shmendrik' afterwards."