Where does “man o' war” come from?

man o' war (English) comes from English MAN, from English manual, from Middle English manuel, from Anglo-Norman manuel, from Old French manual, from Latin manuālis, from Latin manus, from Proto-Italic manus — human being; man; hand.

Ancestry of “man o' war”, step by step

man o' war traces back through 3 separate lines of ancestry.

via English MAN

Step	Language	Word	Meaning
1	English	MAN	Initialism of Metropolitan Area Network
2	English	manual	A handbook; A booklet that instructs on the usage...
3	Middle English	manuel	—
4	Anglo-Norman	manuel	manual; done with the hands; handle; manual;...
5	Old French	manual	—
6	Latin	manuālis	hand
7	Latin	manus	hand; bravery, valor; violence, fighting
8	Proto-Italic	manus	hand
9	Proto-Indo-European	man-	human being; man; hand

via English o'

Step	Language	Word	Meaning
1	English	o'	Contraction of of; Contraction of on
2	Middle English	O	—
3	Old English	o	ever, always
4	Latin	o	The name of the letter "O"; o!; oh!
5	Etruscan	𐌏	—
6	Ancient Greek	ο	Lower-case omicron (ὂ μικρόν), the 15th letter of the ancient Greek alphabet. It represented the close-mid back rounded vowel. It is preceded by ξ and followed by π
7	Phoenician	𐤏	ayin; ʿayin
8	Egyptian	𓁹	—

via English War

Step	Language	Word	Meaning
1	English	War	Preceded by [[the#Article
2	Middle English	werre	War in general; the practice of fighting between...
3	Old Norse	verri	comparative degree of illr, worse; worse
4	Proto-Germanic	wirsizô	comparative degree of *ubilaz; worse
5	Proto-Indo-European	wers-	to wipe; peak, height
6	Proto-Indo-European	wer-	to burn; to cover, heed, notice; squirrel

Every word from Proto-Indo-European man- →Every word from Proto-Italic manus →Every word from Latin manus →