Entries linking to Egbert
Old English ecg "corner, edge, point," also "sword" (also found in ecgplega, literally "edge play," ecghete, literally "edge hate," both used poetically for "battle"), from Proto-Germanic *agjo (source also of Old Frisian egg "edge;" Old Saxon eggia "point, edge;" Middle Dutch egghe, Dutch eg; Old Norse egg, see egg (v.); Old High German ecka, German Eck "corner"), from PIE root *ak- "be sharp, rise (out) to a point, pierce."
Spelling development of Old English -cg to Middle English -gg to Modern English -dge represents a widespread shift in pronunciation. To get the edge on (someone) is U.S. colloquial, first recorded 1911. Edge city is from Joel Garreau's 1992 book of that name. Razor's edge as a perilous narrow path translates Greek epi xyrou akmes. To be on edge "excited or irritable" is from 1872; to have (one's) teeth on edge is from late 14c., though "It is not quite clear what is the precise notion originally expressed in this phrase" [OED].
The Germanic word was commonly used to form given names, and figures in the etymology of Robert, Albert, Bertha, Egbert, Gilbert, Herbert, Hubert, Lambert. In modern German it survives in names only (Albrecht, Ruprecht) and has been otherwise lost.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhrajate "shines, glitters;" Lithuanian brėkšti "to dawn;" Welsh berth "bright, beautiful."