when parish registers were first introduced, the church pretty much ran everything administration wise in a town or village, this included the collection of the rates and the distribution of parish relief, (or income support). To qualify for support from a parish a person had to qualify by either birth or settlement that they had a right to the relief. When a woman married, she would be under the support of her husband, but if her husband died and she had no means of support, she would throw herself on the mercy of the parish. If she was 'not of this parish' on her marriage entry, her home parish would have to bear the responsibility and she would infact be sent back to her home parish, unless she was able to secure another marriage pretty quickly . oh and children of such a marriage would be sent packing with their mother by the churchwardens just so that they did not become a burden, if the deceased husband did not leave a will and his widow could not afford the administraion fees she lost her home too. So, 'of this parish' was a very important status from the 1500s until the early 1800s.