My theory is this: The "Stock" in Mary Stock was a mis-transcribed "Slack" from some almost illegible source that someone construed as her maiden name, when it wasn't. Several collections from Ancestry.com show Mary's actual maiden name to be Lewis, 1661-1734, dau. of John Lewis and Ann Lanphere. In FamilySearch (my primary site), there is a Mary Stock m. to William Slack, but her birth record source shows as b. 1645 in England. Impossible to believe she was then, but only married in 1683 in Massachusetts and began having children up to 1692. I think Mary Stock is a totally fictitious person that has gained some semblance of legitimacy through sheer repetition of the original mistake. Show me a PRIMARY source record that proves otherwise! Sad to say, I simply cannot find that primary source record ... yet ... proving either Mary Lewis or Mary Stock as the wife of William Slack.