A bag carried on the back, typically by hikers or soldiers.
From Low German 'knappsack', combining 'knappen' (to eat) and 'sack' (bag). Originally referred to a soldier's food bag, later expanding to any portable carry-all for travelers.
The knapsack problem in computer science—determining the optimal items to pack given weight constraints—is one of the most studied optimization challenges. It perfectly captures the human dilemma of choosing what's essential when resources are limited.
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