I notice in the parish registers from the 1600s or 1700s that Joan, Jon and Jane seem to be used interchangeably of the same person. I am aware that spellings vary quite widely, but the equation of Joan and Jane puzzles me. As girls were often named after their grandmothers, a name can help in identifying the right family, but Jane doesn't seem the right choice for naming a girl after Joan. Any light on this puzzle?