An example of a knapsack is a schoolbag.
My sleeping bag fell off my backpack into the water, while we were knapsacking up the mountain.
Origin of knapsack
- Probably Low German Knappsack knappen to bite (probably of imitative origin) Sack bag (from Middle Low German sak) (from Old High German sac) (from Late Latin saccus sack1)
From American Heritage Dictionary of the English Language, 5th Edition