This is an anglicized form of the Olde Gaelic O' Glasain or O' Gliasain. The Gaelic prefix "O" indicates "male descendant of", plus the personal byname Glasain, from "glas" literally meaning "green", but used here in the sense of inexperienced. This sept belonged to the ancient territory of Mac Ui Bhriain Aradh's country, that is the area between Nenagh and Lough Derg on the border of North County Tipperary. The Gleesons were of the same stock as the O'Donegans, whose name derives from the Gaelic 'donn' meaning brown or dark. The O' Donegans originally belonged to Muskerry, (north-west and central Cork) and in the 1659 census of Ireland the Gleeson name, under the variant spellings Glisane, Glison, Gleasane, O' Glassane etc., is well recorded in conjunction with O' Donegan in Counties Tipperary, Clare and Limerick. On April 11th 1846 Michael Gleeson, aged twenty two years, embarked from the part of Cork on the ship "Adirondack" bound for New York. He was a famine immigrant into America. Father William Gleeson of Irish stock was called the "founder of the church in California". The first recorded spelling of the family name is shown to be that of O' Glissane, which was dated circa 1600, in the "Records of Extensive Landowners in County Tipperary", during the reign of Queen Elizabeth 1, known as "Good Queen Bess", 1558 - 1603. 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.