Recorded in a number of spellings, as shown below, this is an English surname although one ultimately of French origins. It is a diminutive form of one or more of the personal names Giles, Julian or William, all introduced into the British Isles at or after the famous Conquest of England in 1066. Over the centuries the origins have become confused to the point where it is no longer possible to assign separate derivations to modern surname holders. The current known spellings include Gillard, Gilliard, Gillatt, Gilliatt, Gillyatt, Gillott, Gillyett, Gilyott, Jillett and Jellett, and others. Giles is ultimately from the Greek word "aigidion", meaning kid. When introduced it was as Gille, with the then diminutive forms of Gillet and Gillot, as in Gillot de Lackenby of Yorkshire in the year 1250, and Peter Giliot of Kirkstall, also Yorkshire, in 1333. Julian, and the female form Gillian, are from Juppiter, the supreme god, whose name is akin to words meaning sky, light, or day. From this derived the diminutives Gallard, Gillard and Gilliatt, as in Henry Gillard of Nottinghamshire in 1273. William derives from the French and earlier German Guillame from the wil", meaning desire or conviction and "helm", protection, as in Guylote Belebonche in London in 1319. The first recorded spelling of the family name in any spelling may be John Gilot of Durham in the Assize Rolls of the county in 1243, during the reign of King Henry 111rd, 1216 - 1272. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as the Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.