Errors in writing, voluntary changes by the bearers, modifications for language reasons... There are many reasons why the surname Gajap may have undergone changes or modifications, and from those modifications, surnames similar to Gajap may have appeared, as we can see.
Discerning whether the surname Gajap or any of the surnames similar to Gajap came first is not always easy. There are many reasons that could have led to the surname Gajap being written or pronounced differently, giving rise to a new, different surname Gajap with a common root.