Where does “fen” come from?

fen (Middle English) comes from Old English fenn, from Old English tūn, from Proto-West Germanic tūn, from Proto-Germanic tūną, from Gaulish dunum, from Proto-Celtic dūnom, from Proto-Indo-European dʰewh₂- — smoke; mist, haze.

fen (Middle English): fen, bog, swamp; dirt, muddiness; dung, feces

Definitions

fen, bog, swamp; dirt, muddiness; dung, feces

Ancestry of “fen”, step by step

fen traces back through two separate lines of ancestry.

via Old English fenn

Step	Language	Word	Meaning
1	Old English	fenn	mud; fen, marsh
2	Old English	tūn	enclosure, yard; place; dwelling
3	Proto-West Germanic	tūn	fence
4	Proto-Germanic	tūną	fence; enclosure
5	Gaulish	dunum	fort; hill, hillfort
6	Proto-Celtic	dūnom	stronghold, rampart
7	Proto-Indo-European	dʰewh₂-	smoke; mist, haze

via French fiente

Step	Language	Word	Meaning
1	French	fiente	droppings
2	Vulgar Latin	*femita	—
3	Latin	femus	—
4	Latin	fimus	Alternative form of fimum; first-person plural...

Words derived from “fen”

Every word from Proto-Indo-European dʰewh₂- →Every word from Proto-Celtic dūnom →Every word from Gaulish dunum →