Where does “Guernsey” come from?

Guernsey (Portuguese) comes from English Guernsey, from Old Norse ey, from Proto-Norse *ᚨᚢᛃᚢ, from Proto-Germanic awjō, from Proto-Germanic agwjō, from Proto-Indo-European h₂ékʷeh₂ — water.

Ancestry of “Guernsey”, step by step

Step	Language	Word	Meaning
1	English	Guernsey	A cow of a breed of dairy cattle originally bred...
2	Old Norse	ey	always, ever; island
3	Proto-Norse	*ᚨᚢᛃᚢ	—
4	Proto-Germanic	awjō	floodplain; meadow; island
5	Proto-Germanic	agwjō	—
6	Proto-Indo-European	h₂ékʷeh₂	water

Every word from Proto-Indo-European h₂ékʷeh₂ →Every word from Proto-Germanic agwjō →Every word from Proto-Germanic awjō →