The combination of "knap sack and back pack", this term can is only used, and understood in Thunder Bay, ON (Canada), and if used anywhere else.. speaker will be mocked.
Kid 1: "My mom bought me a kick ass packsack for the new school year!"
Kid 2: "Your mom's a whore."
An annoying term used by people who mistake the common term backpack for packsack.
Rick: That's a nice packsack Bill!
Bill: Packsack? LOL