This interesting surname is an Anglicized form of the Gaelic O Callanain meaning "descendant of Callanan", a personal name of uncertain origin. The surname is found mainly in county Clare using the spelling Callinan, and in counties Galway and Cork using the spelling Callanan. The main sept was a medical family to the McCarthy's of Carbery, Co. Cork. The surname dates back to the early 15th Century, (see below). Further recordings include one Angus O' Callanan (1475) who was the chief scribe of the Book of Lismore (otherwise called the Book of the McCarthy Reagh). Six of the name bearers appear in King James 1's army list, one being surgeon in Hon., Nicholas Browne's regiment. One Charles Callenan married Elizabeth Busley on December 13th 1712 at St. Martin-in-the-Fields, Westminster, and Mary Callinan married James Hanneen on February 17th 1867, at Killofin, Co. Clare, Ireland. One Joseph Jeremiah Callanan (1795 - 1829), the Co. Cork poet was buried in Lisbon. The best known of his works in ireland and English is "Gougaune Barra". The first recorded spelling of the family name is shown to be that of Angus O' Callanan, which was dated 1403, wrote a medical treatise for Mac Carthy Reagh, during the reign of King Henry 1V, of Bolingbroke, 1399 - 1413. 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.