Hee! I was trying to come up with a unique nickname, one that wouldn't come up between them when Dean didn't have his memories and I thought that Shame or Shay were common enough that they might. Plus - I think there are loads of people that would think "Seem" when they see the name for the first time. So, I thought maybe Dean would give Seamus shit over his name by mispronouncing it all the time. Thus - Seem was born :D

There's plenty of both to come with, of course, happiness there too :D.