Reconstruction:Proto-Germanic/ga-

• *gą-

From Proto-Indo-European *ḱóm (“with, near, by, along”). Cognate with Latin co-, con-, prefix forms of cum (“with”). The irregular change from expected **ha- to *ga- is probably due to either due to influence from Proto-Indo-European *gʰo- or the original prefix itself being considered "unstressed" by Germanic speakers, which would activate Verner's law and cause the shift (Compare *uz).^[1]

*ga-

1. Indicates association or togetherness; co-.
2. Indicates completeness or wholeness. In verbs, also indicates perfectivity (a finished action). In nouns, expresses intensive or perfective meaning.

• *gagana
• *gaganą

In Old Norse, *ga- only survives as a fossil in a few words. Its semantic function was, however, retained perfectly by the particle of.

• Proto-West Germanic: *ga-
  • Old English: ġe-, i- — Late West Saxon, ġæ-, ġi- — Northumbrian, ie- — Kentish, ᚷᛁ- (ġi-), ᚸᛖ- (ge-)
    • Middle English: ge-, ȝe-, i-, y-
      • English: a-, y-, i- (obsolete or dialectal)
      • Yola: ee-
  • Old Frisian: ge-, gi-, je-, ie-, e-, i-, a-
    • Saterland Frisian: ge-
    • West Frisian: ge-
  • Old Saxon: gi-, i-, ge-, ga-
    • Middle Low German: ge-
      • Low German: ge-, e-, je-
  • Old Dutch: gi-, ge-
    • Middle Dutch: ghe-, ge-, (West-Flanders) i-, y-
      • Dutch: ge-
        • Afrikaans: ge-
      • West Flemish: ge-, e-
  • Old High German: gi-, ga-, ki-, ka-
    • Middle High German: ge-
      • Alemannic German: g- or ge- (euphonic)
      • Bavarian: g-
      • German: ge-, g-
      • Luxembourgish: ge-
      • Vilamovian: gy-
      • Yiddish: גע־ (ge-)
• Old Norse: g- (non-productive)
  • ⇒ Old Norse: gnógr, glíkr, greiðr, greiða, granni
• Gothic: 𐌲𐌰- (ga-)
• Vandalic: *ga-