https://www.behindthename.com/name/gibbon/submitted https://www.behindthename.com/name/gibbon/submitted diminutive of Gilbert. My guess is its just like Robin:

https://www.behindthename.com/name/gibbon/submitted https://www.behindthename.com/name/gibbon/submitted diminutive of Gilbert. My guess is its just like Robin: Rob + kin -> Robkin -> Robin Gib + kin -> Gibkin -> Gibbon