This extraordinary Irish surname is believed to be a development form of the Gaelic "Raghellach" which translates as "the son of Gregarious race". The "root" is also found in the forms (Mac)Crilly, (Mac)Crawley, (O) Crawley, and "(O) Reilly. It is also possible that the name could derived from Mac Fhearghail, the son of "super choice" - this type of personalised compound being very popular in early Gaelic-Celtic etymology. The "modern" spelling is a late developer. The 16th Century spelling being Mac Grealis, or Mac Nealis, what is beyond argument is that the name originates in Ulster and local recordings include Ann McCrillis who married John Lusk on May 22nd 1823, at Ballymoney, Co. Antrim, which appears to be the "home" of the name. The first recorded spelling of the family name is shown to be that of William McCrillis, which was dated November 13th 1815, a witness at Ballymoney Parish Church, Co. Antrim, during the reign of King George 111, "Farmer George", 1760 - 1820. 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.