mid-15c., "edge of web or cloth so finished as to prevent raveling," apparently literally "its own edge," a corruption of self + edge (n.); on analogy of Middle Flemish selvegge (compare also Low German sulfegge; Dutch zelfkant, from kant "border;" Middle High German selbende, German Selbend, literally "self-end").
Entries related to selvage
Old English self, seolf, sylf "one's own person, -self; own, same," from Proto-Germanic *selbaz (source also of Old Norse sjalfr, Old Frisian self, Dutch zelf, Old High German selb, German selb, selbst, Gothic silba), Proto-Germanic *selbaz "self," from PIE *sel-bho-, suffixed form of root *s(w)e-, pronoun of the third person and reflexive (referring back to the subject of a sentence), also used in forms denoting the speaker's social group, "(we our-)selves" (see idiom).
Trying to define yourself is like trying to bite your own teeth. [attributed to Alan Watts, who did often use the image in this sense in his talks, if not in these exact words]
Its use in compounds to form reflexive pronouns grew out of independent use in Old English. As a noun from early 14c.
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].
It forms all or part of: acacia; acanthus; accipiter; acer; acerbic; acerbity; acervate; acervulus; acescent; acetic; acid; acicular; acme; acne; acrid; acridity; acrimony; acro-; acrobat; acromegaly; acronym; acrophobia; acropolis; acrostic; acrylic; acuity; aculeate; acumen; acupressure; acupuncture; acute; aglet; ague; Akron; anoxic; awn; coelacanth; dioxin; deoxy-; eager; ear (n.2) "grain part of corn;" edge (n.); egg (v.) "to goad on, incite;" eglantine; epoxy; ester; exacerbation; hammer; hypoxia; mediocre; oxalic; oxide; oxy-; oxygen; oxymoron; paragon; pyracanth; paroxysm; selvage; vinegar.
It is the hypothetical source of/evidence for its existence is provided by: Greek akros "at the end, at the top, outermost; consummate, excellent," akis "sharp point," akros "at the farthest point, highest, outermost," akantha "thorn," akme "summit, edge," oxys "sharp, bitter;" Sanskrit acri- "corner, edge," acani- "point of an arrow," asrih "edge;" Oscan akrid (ablative singular) "sharply;" Latin acer (fem. acris) "sharp to the senses, pungent, bitter, eager, fierce," acutus "sharp, pointed," acuere "to sharpen," acerbus "harsh, bitter," acere "be sharp, be bitter," acus "a needle, pin," ocris "jagged mountain;" Lithuanian ašmuo "sharpness," akstis "sharp stick;" Old Lithuanian aštras, Lithuanian aštrus "sharp;" Old Church Slavonic ostru, Russian óstryj "sharp;" Old Irish er "high;" Welsh ochr "edge, corner, border;" Old Norse eggja "goad;" Old English ecg "sword;" German Eck "corner."