The word is almost the same in Norwegian and Swedish too.
http://en.wikipedia.org/wiki/Backpack
To answer your question Bree I have a changing collection of rucksacks. I like to try different ones but I never have more than 2 or 3 at any one time.
At the moment I have the one I just bought to give to my daughter;
then a 1970's shortback "H" external frame rucksack;
my "soft" comfy everyday rucksack based on a wartime german design
and a Swedish ex-army surplus military backpack, which is crap.
The ones I am looking out for are old longback H frame and A frame rucksacks, I used to have them years ago but now they are very rare, nobody makes them any more.