Double-barrelled surnames, usually created following a marriage between two families, have no overall meaning as a unit, but the separate parts have their own meaning and derivation. In this instance, Leith is of medieval Scottish origin, and is a locational name from the coastal town of Leith near Edinburgh, which is so called from the river at whose mouth it stands. The river name is derived from the Gaelic "lite", meaning "wet", omparable to the Welsh "llaith", damp, moist. Gilbert de Leth, "Custumar" or collector of customs in Edinburgh in 1327, was the first recorded bearer of the name. One, William de Lethe was burgess of Aberdeen, which he represented in parliament in 1367. The surname Harvey has two distinct possible origins; firstly, it may derive from the Old Breton personal name "Aerviu" or "Haerviu", composed of the elements "haer", battle, carnage and "vy", worthy. This name was introduced into England by Breton followers of William the Conqueror and appears in the Domesday Book of 1086 as "Herve". It may also be an Anglicized form of the Old GAelic Irish "O HAirmheadhaigh", "descendant of Airmheadhach", a byname thought to mean "herder of cattle". Notable namebearers were William Harvey who discovered the circulation of the blood circa 1616, and Sir James Leith (1763-1816), lieutenant-general, 1813; governor of the Leeward islands 1814 and G.C.B., 1815. The first recorded spelling of the family name is shown to be that of William Hervi, which was dated 1190, in the "Kalendar of Bury St. Edmunds", Suffolk, during the reign of King Richard 1st, "Richard 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.