haversack vs back pack

haversack and back pack both are nouns.

Word	Noun	Adjective	Verb	Adverb
haversack	Yes	No	No	No
back pack	Yes	No	No	No

As nouns, haversack and back pack are synonyms defined as:

haversack and back pack: a bag carried by a strap on your back or shoulder

Other synonyms of haversack include backpack, knapsack, packsack, rucksack.

haversack (noun)	back pack (noun)
a bag carried by a strap on your back or shoulder	a bag carried by a strap on your back or shoulder