Recorded in many forms including O' Longain, Longain, Lanahan, Langan, Lanigan, Lannigan, Lonnigon, Lenaghan, and Lenihan, this is an Irish surname. However spelt in Ireland they originate from O' Longain or O' Lennachain, and it is possible both derive from the early Norse-Viking and later Gaelic word "long". If so the names in a transfrred sense refer to a ship and hence were bi-names for a sailor, or more precisely, the male descendant of a sailor, who may well have been a Viking. O' Leannachain was originally the name of an Irish sept situated in Roscommon, while two distinct septs of O' Longain existed, one in County Mayo, and a branch of the Ulster sept in County Armagh; the other in Counties Cork and Limerick. They were erenaghs of hereditary lay lords, responsible for the maintenance of church lands, and some later adopted the surname of Long. As Langan or Lenihan the surnames were introduced into England by Irish famine immigrants (1845-1847) and probably through differences in pronunciation or because they wanted the name to sound English or Scots, also became Lanahan, a name not apparently recorded in Ireland. The first recorded spelling of the family name is shown to be that of Maelciaran O'Lenechan. This was dated 1249, in the "Annals of Loch Ce". Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.