Where does “indoor” come from?

Indoor comes from English in and door, which derives from Middle English dore, Old English dora, Proto-Germanic durz, and Proto-Indo-European dʰwer-, meaning an opening or passage.

indoor (English): Situated in, or designed to be used in, or...

Definitions

Situated in, or designed to be used in, or...

Ancestry of “indoor”, step by step

indoor traces back through two separate lines of ancestry.

via English door

Step	Language	Word	Meaning
1	English	door	A portal of entry into a building, room, or...
2	Middle English	dore	A door or gate structure barring an entrance
3	Old English	dora	bumblebee
4	Proto-Germanic	durô	bumblebee, humming insect
5	Proto-Indo-European	dʰer-	to support; to hold

via English in

Step	Language	Word	Meaning
1	English	in	Used to indicate location, inclusion, or position...
2	Middle English	in	Any kind of accomodation; particularly; A home or...
3	Old English	in	in; Alternative form of inn
4	Proto-West Germanic	*in	—

Words derived from “indoor”

Every word from Proto-Indo-European dʰer- →