What does it mean?

[Robbyn]

Is this true?   A friend recently told me that in Jewish tradition the head of the household would fold his napkin to let everyone else know he was coming back to finish his dinner, but, if not, he would just lay it down so everyone knew he wasn't returning to the table.  This is supposedly why, at a restaurant, we do essentially the same.  Does anyone know the answer?

[DSB]

A quick Google search shows that this is probably a myth:
     http://www.truthorfiction.com/rumors/f/folded-napkin.htm

[marco23]

I think the same thing you are right.