Complex sentence: The word rucksack is a German loanword mainly used in the UK and in western military forces: in German'der Rücken' means'the back' (the part of the body), and "Sack" for "bag".
Split into simpler sentences: The word rucksack is a German loanword mainly used in the UK and in Western military forces. In German, "der Rücken" means "the back (the part of the body)" and "Sack" for "bag".