Justin, xliii. 5.
 O’Grady, ii. 362; Giraldus, Descr. Camb. i. 11.
 Pennant, Tour in Scotland, i. 311; Martin, 111.
 Richardson, Folly of Pilgrimages, 70.
 Tertullian, de Anima, 57; Coll. de Reb. Hib. iii. 334.
 Campbell, Superstitions, 263; Curtin, Tales, 84.
 Lucan, ed. Usener, 33.
 See examples in O’Curry, MS Mat. 383 f.
 Miss Hull, 19, 20, 23.
 LU 55.
 RC xii. 98, xxi. 156, xxii. 61.
 RC xv. 432; Annals of the Four Masters, A.M. 2530; Campbell, WHT iv. 298.
 See “Adamnan’s Second Vision.” RC xii. 441.
The Irish geis, pl. geasa, which may be rendered by Tabu, had two senses. It meant something which must not be done for fear of disastrous consequences, and also an obligation to do something commanded by another.
As a tabu the geis had a large place in Irish life, and was probably known to other branches of the Celts. It followed the general course of tabu wherever found. Sometimes it was imposed before birth, or it was hereditary, or connected with totemism. Legends, however, often arose giving a different explanation to geasa, long after the customs in which they originated had been forgotten. It was one of Diarmaid’s geasa not to hunt the boar of Ben Gulban, and this was probably totemic in origin. But legend told how his father killed a child, the corpse being changed into a boar by the child’s father, who said its span of life would be the same as Diarmaid’s, and that he would be slain by it. Oengus put geasa on Diarmaid not to hunt it, but at Fionn’s desire he broke these, and was killed. Other geasa—those of Cuchulainn not to eat dog’s flesh, and of Conaire never to chase birds—also point to totemism.
In some cases geasa were based on ideas of right and wrong, honour or dishonour, or were intended to cause avoidance of unlucky days. Others are unintelligible to us. The largest number of geasa concerned kings and chiefs, and are described, along with their corresponding privileges, in the Book of Rights. Some of the geasa of the king of Connaught were not to go to an assembly of women at Leaghair, not to sit in autumn on the sepulchral mound of the wife of Maine, not to go in a grey-speckled garment on a grey-speckled horse to the heath of Cruachan, and the like. The meaning of these is obscure, but other examples are more obvious and show that all alike corresponded to the tabus applying to kings in primitive societies, who are often magicians, priests, or even divine representatives. On them the welfare