Come to that, I'm not sure I've ever heard the words "sailor's palm" mentioned outside my mother's house. Is it an object the existence and use of which is known to all? Is it ultra-obscure? Or - as I shrewdly suspect - somewhere in between? There's only one way to found out...
Do you know what a sailor's palm is (without looking it up)?
Of course! Doesn't everyone?
Sounds vaguely familiar, but I'm not sure...
It means nothing to me.
What's the most obscure object in your house?