Webster’s Revised Unabridged Dictionary · 1913
Knapsack
Knap′sack′, n. [D. knapzak; knappen to eat + zak a bag. See Knap, v. t., and Sack.] A case of canvas or leather, for carrying on the back a soldier's necessaries, or the clothing, etc., of a traveler.
And each one fills his knapsack or his scrip With some rare thing that on the field is found. Drayton.