The name rarely bears the prefix nowadays, and is usually rendered Scallan, Scanlan or Scanlon.
It is a variant of the name Ó Scannail derived from the Irish word scannal, originally meaning quarrel, contention, fight, and later, scandal.
One sept is O'Scannlain of Munster and the other is MacScannláin of Oriel, County Louth, neither of which has retained the prefix 0 or Mc in modern times.
The widespread distribution of these names is indicated by the fact that there are six Ballyscanlans in Ireland as well as a Scanlansland and a Scanlan's Island.
Two of these are in County Clare and one in Mayo, which lends colour to the statement that there was also a North Connacht Sept of O'Scanlan.