Exactly as I remember as well. My father, born in west Texas (San Angelo) in the mid '30s did the same thing to me. Growing up in the 60s', after having a haircut when my dad came home from the office, if I said Vinch Rinktums (not sure the spelling) when he saw my haircut but before he said Runktums,then I would avoid that knuckle up the back of the head. And, like mentioned before, once you slept on the new haircut, you were safe. Never understood the tradition, and never thought to ask before he passed. Must have been a west Texas thing. We did grow up with some odd traditions (like setting off fireworks on Christmas eve).