Where does “undefended” come from?

Undefended comes from English defend plus the prefix un-, tracing through Latin unus and ultimately to Proto-Indo-European óynos and h₂ent-.

undefended (English): Not defended

Definitions

Step	Language	Word	Meaning
1	English	defended	simple past tense and past participle of defend
2	English	defend	To ward off attacks against; to fight to protect;...
3	Middle English	defenden	defend
4	Old French	défendre	—
5	Latin	dēfendō	—
6	Latin	dē-	—
7	Latin	dē	—
8	Latin	post	behind; after, since, besides, except; behind,...
9	Latin	poste	ablative singular of postis
10	Proto-Italic	posti	—
11	Proto-Indo-European	pósti	—
12	Proto-Indo-European	pós	afterwards, post; by, at

undefended — Etymology, Origin & Word History | Etymology Explorer