Where does “Northhumbre” come from?

Northhumbre (Middle English) comes from Old English Norþhymbre, from Old English Norþanhymbre, from Old English Humbre — the Humber.

Ancestry of “Northhumbre”, step by step

Step	Language	Word	Meaning
1	Old English	Norþhymbre	—
2	Old English	Norþanhymbre	Northumbia", also "Northumbrians; the...
3	Old English	Humbre	the Humber

Northhumbre — Etymology, Origin & Word History | Etymology Explorer