Thanks for your response and info. With that and some other digging around since my first post, I've concluded that the name was originally Mercer, and that there was an Abiel who came over sometime around 1635, but not on the DEFENSE and not to Hingham...he is not on the passenger list and there is no mention of him in the early annals of Hingham.
But I think Richard in Haverhill was probably his son, and named his own son for his father. Both Richard and his son Abiel were recorded as Mercer, and the named was later changed to Messer.
Just curious...how did my inquiry happen to catch your interest?? Anyway, thanks again, Bill T