Isn’t Rucksacks (m) a German word? I Believe that here Steve Kaufman should have used backpack. Of course, he is talking about a nice travel around Europe, so it is possible that he just wanted to recreate the fact that during his trip he has catch up few new words of other languages… 
For people of Steve’s (and my) generation, a rucksack is a backpack. I still use my trusty rucksack. Backpacks to me are huge unwieldy affairs, with lots of differents parts, a rucksack is a rucksack 
I wore a backpack to university, and I still buy school backpacks for my kids. But most people in Australia know rucksack means the same thing Ah, I see your mother tongue is Canadian French. That might explain why you hadn’t noticed it in English. Good luck with your English learning adventures!
The word “リュックサック(Rucksack)” or “リュック” is more familiar than “backpack” to me.
Yes, ‘der Rucksack’ is a German word.
It consists of two words: der Rücken (= back) + der Sack (=pack).
Thank you for taking the time to explain to me that depending where you are coming from; it is or it isn’t common to talk about a ‘’Rucksack’’ in English !
I am happy to know that I can use this nice German word even with English speakers of the world.
In 1990, I was for an entire year like Steve Kaufman hitchhiking and traveling in France and Germany. ‘’Wo ich auch Deutsh gelernt habe. ‘’ But I always talked about my ‘’sac à dos’’ with people from France and backpack which is also built of 2 words like the German ‘’Rucksack’’ masculine word with the English speakers.
At the beginning of my travel, I was only able to say few words of my high school English learning : my name is Eve, I am coming from Canada, and I am 20 years old, but I was also talking with a lot of Americans in the army about my backpack, and never about my ‘’Rucksack’’.
It is four months later; when I started to learn German from scratch zero, that I realized that ‘’Rucksack’’ was a backpack of any size to shape. https://www.google.ca/search?q=rucksack&espv=2&biw=1280&bih=643&tbm=isch&tbo=u&source=univ&sa=X&ei=o3w6VbS3HO3_sAS13IDwDg&ved=0CBwQsAQ&dpr=1
Yes, my mother tongue is French.
My English isn’t that bad, it do have more trouble with the right pronunciation of few words that are for me still really hard to pronounce properly. Sometimes, I am also scared that my way of building (writing) my sentences will be more with the French than the English structures.
However, if you see that I have done big mistakes, please let me know.
Thank you again and have a nice weekend !