Earliest reference I have found so far

A John Rainbow was left 2d in the will of William Folwell of Chachombe 1552, which is 12 miles from Weedon Beck.

Other Parishs in the area known to have had Rainbows living / born / christened / married in are:-

Sulgrave, Weedon Beck, Weedon Lois, Crick, Long Buckby, Braunston, Bugbrooke, Everdon.

Not far from Banbury which I believe is the link to the Gloc's brach.

Has anybody looked at doing a cluster analysis using the parish and year as variables ?

Another John Rainbow married Mary Smith on 22/05/1720 at Bugbrooke Nth's ( only 3 miles from Weedon Beck, Mary Smith can be traced back through various Abraham Elizabeth Anne and Marys to 1666 still in the same area.