East Dane is an Anglo-Saxon ethnonym which was used in the epic Beowulf.
It was also used in an Anglo-Saxon runic poem describing the first appearance of the god Frey (called Ing, see Yngvi):
:Ing wæs ærest mid Eástdenum
:gesewen secgum, oð he síððan eást
:ofer wæg gewát. wæn æfter ran.
:þus Heardingas þone hæle nemdon.
:Ing was first amidst the East Danes
:so seen, until he went eastward
:over the sea. His wagon ran after.
:Thus the Heardings named that hero.