/ ˈrʌksæk; NAmE / ( BrE ) (also back·pack NAmE , BrE ) noun
a large bag, often supported on a light metal frame, carried on the back and used especially by people who go climbing or walking
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WORD ORIGIN
mid 19th cent.: from German , from rucken (dialect variant of Rücken back) + Sack bag, sack.