The G Word

Is there any reason (other than sheer coincidence) why so many words for "outsider" begin with the letter "G"? See, e.g.:

• Gadje/Gorgio – Roma (people) – Romany
• Gaijin – Japan – Japanese (although these days gaikokujin is becoming popular because of its "softer" meaning.)
• Gall – Irish
• Gentile – Mormonism – Judaism – Latin
• Giaur – non-Muslim (infidel)
• Goy – Judaism – Hebrew
• Gweilo – Hong Kong – Cantonese

Source:Nationmaster.com. All those except "gentile" and "goy" (i.e., all those in Italics) are deemed not fully assimilated into English.