A native or inhabitant of the northern part of the early English kingdom of Mercia, south of the River Humber and north of the River Trent. Also more widely: a native or inhabitant of England south of the River Humber.
Of or relating to northern Mercia. Also more widely: of or relating to England south of the River Humber.
Early 18th century; earliest use found in Nicholas Tindal (1687–1774), historical writer and translator. From south + -humbrian, after Old English Sūðhymbre Southumbrians.