Recorded as O' Crean, Cregan, Creggan, Cregeen, Cregin, this is a medieval Irish surname. It is a form of either of two Old Gaelic names: O' Croidheagain of Connacht and O' Croidheain of County Donegal, the latter with a branch in County Sligo. The prefix O' indicated male descendant of, and the personal bynames "Croidheagain" and "Croidheain" derive from "croidhe", meaning heart, used as a term of endearment. The former sept name is usually Cregan in Sligo, Creegan in Leitrim and Roscommon, and O' Crean, Creaghan and Crehan in other areas. The O' Croidheain of County Donegal are of the Cenel Eoghain, that is they belong to that group of people descended from Eoghan, son of Niall of the Nine Hostages. They are twice mentioned in the Annals of the Four Masters as wealthy merchants in Donegal 1506, and in Sligo 1572. Examples of recordings taken at random from surviving registers include Mary Creegan born at Shanmullagh, County Longford, on June 1st 1792, another Mary, this time the daughter of Richard Cregin, christened at Eastleach Turville, Gloucestershire, England on April 6th 1794, and on December 10th 1810, the marriage of Mary Creggen to David Woodbaridge St. Mary-le-Bone, Marylebone Road, London. The first recorded spelling of the family name is shown to be that of Teag O' Crean. This was dated 1506, in the "Annals of the Four Masters". Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.