Where does “Gannon” come from?

Gannon is an English surname derived from Irish Mag, a patronymic prefix whose ultimate origin and meaning are unattested.

Ancestry of “Gannon”, step by step

StepLanguageWordMeaning
1IrishMag Fhionnáin—
2IrishFionnfair (of hair or complexion)
3Old Irishfindwhite
4Proto-CelticKʷennowindoswhite-headed, white-faced
5Proto-Celticwindoswhite
6Proto-Indo-Europeanwindo-—
7Proto-Indo-Europeanweyd-to see
Every word from Proto-Indo-European weyd- →Every word from Proto-Indo-European windo- →Every word from Proto-Celtic windos →