The information given on this site:
http://www.whatsinaname.net/female-names/Jessie.htmlmay help researchers who have, as I had, met a brick wall over the name Janet and/or Jessie. The 2 names have been synonymous for at least 2 centuries. A girl baptised Janet often becomes Jessie in subsequent records, and slightly more unusually, the opposite happens, as in the case of my gg grandmother, baptised Jessie 1827 in Canonbie, daughter of Abel Armstrong and Isabella Taylor, who is known as Janet for the rest of her life.