Where does “treetop” come from?

Treetop comes from English tree and top, with tree deriving from Middle English tre, from Proto-Germanic trewwō, ultimately from Proto-Indo-European dóru meaning wood or tree.

treetop (English): The crown or uppermost branches of a tree

Definitions

The crown or uppermost branches of a tree

Ancestry of “treetop”, step by step

Step	Language	Word	Meaning
1	English	top	The highest or uppermost part of something; A...
2	Middle English	top	The summit or top of something, especially a...
3	Old English	topp	—
4	Proto-West Germanic	*topp	—
5	Proto-Germanic	tuppaz	tuft, plait; top, summit
6	Proto-Indo-European	dumb-	tail, rod, staff, pole, penis; tail, rod, staff,...

Every word from Proto-Indo-European dumb- →

treetop — Etymology, Origin & Word History | Etymology Explorer