The terms “Gaffer” and “Gammer” did not break into print before the latter end of the sixteenth century, but both must have been in common dialectal speech many long years earlier.
And, of course, dispute reigns as to what were the original words.
As now used, almost wholly only in rural England, they are usually terms of address, respectively, to an elderly man and an elderly woman.
The present consensus is that they have gradually evolved as contractions of godfather and godmother, but there is also a strong belief that the original forms were grandfather and grandmother.