This unusual name has two possible derivations, the first of which is Scottish and is particularly associated with Aberdeenshire. One Thomas Cay was tenant of "Tumbelle" in Stratdee, in 1539, (Exchequer Rolls of Scotland), while William Cay was 'Cautioner' (one who stands security for another) for one George Reoche in 1602. The Scottish name is thought to be derived from a medieval (and earlier) nickname from the Northern Middle English "kay". (Old Norse "ka") meaning "jackdaw". This derivation could also apply in England, of course. The second possible source is from another nickname this time from the northern and eastern dialect word "kei", which gave rise to a nickname for a left handed (and therefore possibly clumsy) person. One Benedict Cay is recorded in the Suffolk Pipe Rolls of 1297. The first recorded spelling of the family name is shown to be that of Geoffrey Cai. which was dated 1197, The Norfolk Pipe Roll. during the reign of King Richard I, The Lionheart, 1189 - 1199. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.