Each of the words has its ultimate origin in med. Lat. Janua |Genoa', and all three passed into English from French, which has variants of the place-name with a spelling, as in OF janne(s), and with e spelling, as in (antecedents of) F Genes.(9)
Whichever may be the correct explanation of the origin of the form geances, there seems to be quite sufficient evidence in the records of forms descended from med. Lat. Janua with and without -s in the stem and with (the reflexes of) ME /a:/ or /[Epsilon]: as stressed vowel to establish between geance and jane a credible formal association.