<human>: Condense the text into a few key points

Yesterday: I was with my wife walking the dog when we came across this older gentleman, and we got to talking.  It turns out he's from the same town as my mother's family, and I say as much.  He then asks me what my grandfather's name is...and I draw a complete blank.  

My grandfather had died before I was born, so I didn't ever know him as "grandpa" - my mother always called him by his first name and I can't remember what it is!  Embarrassed, I make a lame excuse and we move on.  

Later that evening I'm telling my sister's about the encounter, expecting some group self-deprecating humor, some "yeah, it's hard since we never new him" etc.  But instead they are just looking at me, and it was making me uncomfortable. 

"You're fucking kidding, right?" my oldest sister asks.  I'm dumbfounded - I don't think it's THAT odd I can't remember.

Then they both say in unison "You're named after him, you DUMBASS!!"
<bot>: I forgot that I was (middle) named after my grandfather, and gave my sisters ammo for teasing me for years to come.  Sorry Grandpa Norman.