How I know my Grandfather's shoe size

I have all sorts of useless information floating around in my head. Who knows why I know my phone number from when I was 10,  but I still have to look up my son's phone number.  I do however know why I know that my grandfather wore a size 10-1/2 shoe. My grandfather could never be accused of not telling it to you straight. He spoke in a certain dialect that I have heard called "the King's English".  We grew up hearing words and stories  most kids didn't hear until they snuck into R movies. (No PG-13 in those days).   Grandpa's favorite word was GD.  Grandma had a hard time deciding if she liked S**T or A*****E better. Probably depended on the situation.  If Lou Holtz was in the conversation it was most likely Son of a B***H.  I always tell people it isn't really my fault that I cuss like a sailor.  It is in my blood.  So, how do I know Grandpa's shoe size?  Whenever one of us kids wasn't doing what we were supposed to he would say in his gruffest Grandpa Little voice " Get a move on unless you want a size 10-1/2 boot up your ass".