Northman vs berserk

Northman and berserk both are nouns.

Word	Noun	Adjective	Verb	Adverb
Northman	Yes	No	No	No
berserk	Yes	Yes	No	No

As nouns, berserk is a hyponym of Northman; that is, berserk is a word with a more specific, narrower meaning than Northman:

Northman: an inhabitant of Scandinavia
berserk: one of the ancient Norse warriors legendary for working themselves into a frenzy before a battle and fighting with reckless savagery and insane fury

Other hyponyms of Northman include Viking, berserker.

Northman (noun)	berserk (noun)
an inhabitant of Scandinavia	one of the ancient Norse warriors legendary for working themselves into a frenzy before a battle and fighting with reckless savagery and insane fury

Northman (adjective)	berserk (adjective)
	wildly frenzied and out of control