A “Geis” is something we encounter a lot in Celtic mythology, and it is a fascinating thing. We find that such and such a warrior was under a geis and thus was prevented from pursuing a particular course of action. There was a sort of duality to a geis’ nature, at once a blessing but also a curse. The geis was an all-powerful thing, and woe betide you if you broke it for to do so often resulted in death or at the very least grave misfortune. On the other hand, the observing of one’s geis was believed to bring power and something the bearer tried their best to uphold.

A “Geis” translates literally as a “Request,” derived from the verb “guided” (“to pray”), and is interpreted in the sense of a request. It wasn’t however something the bearer ever asked for, rather it was placed upon them and often without their prior knowledge. The main sources for us to look at the geis are early Irish literature and they are most numerous in the Ulster Cycle

Every Irish chieftain or personage of note had a geis peculiar to himself and one which he must not contravene. They were bestowed in a variety of ways and served a range of purposes, and were laid on an individual to ensure they avoided disaster, dishonour, or shame. All the examples of gessi we see in the sources apply to people of high status and as such they had much to live up to. The geis, or “gessi” in the plural, bound the bearer’s hands and feet. The geis is most often what becomes the Achilles heel in Celtic myth, and we see numerous examples of this being played out.

Druids were of course the initiators, and they were bestowed on the individual at birth or conception or at a time of inhiation. Oftentimes too, it was the women who placed geis upon their men. Aoife imposed three gessi on Connla, her son with Cú Chulainn:

1.          He could not turn back once he started his journey.

2.         He must never refuse a challenge.

3.         He must never tell anyone his name.

Conchobar’s son Cormac had his gessi laid on him at birth by a druid. Cú Chulainn himself laid gessi on his own son Connla. The legendary king Conaire’s gessi were given to him by his father. They can be viewed as a rite of passage.

Aoife’s example shows us of how the placing of a geis can lead to tragedy even when it is not violated. Aoife sent Connla to seek out his father. Even though he was only aged seven he was a child of extraordinary skill and defeated all the Ulster heroes who met him. Connla was seen as a threat by Cú Chulainn and he demanded to know his identity. Because of the geis placed on him by his mother, he refuses to identify himself which resulted in his own father, Cú Chulainn, killing him in single combat with the Gáe Bulg. 

Sovereigns and Kings were not exempt from the geis, in fact gessi governed the kings’ behaviour in all aspects of his life. Kings were expected to be in “rop sogeis” – “let him be of good (i.e. keep) taboos.” A man could only be king if he observed and upheld the gessi associated with his status and be without gessi that would disqualify him from the kingship during his tenure e.g. be without blemish, show good judgement and generosity etc. Sometimes the gessi were eminently sensible, the King of Emania for example, was forbidden ever, when alone, to attack a wild boar in his den. (Wild boars were very dangerous and best hunted in company, and perhaps there were many such wild animals in his kingdom) The King of Ireland could not let the sunrise catch him lying in his bed at Tara, and as such this made him a good timekeeper.  King Conchobar mac Nessa had the “geis of the king” the right to the first night with any marriageable woman and the right to sleep with the wife of anyone who hosted him. (Not a bad gig one could argue.)

he king of Connacht, had these prohibitions laid on him:

“There are prohibitions for the king

of Connacht, let him observe them in his country;

a circuit around Cruachain on the day of Samain

is not lucky, rather is it disastrous.

To contend with the rider of a grey horse

in Áth Gallda between two posts,

to tryst at Segais in addition,

to sit on the burial mounds of Maine’s wife.

Let him not go in a coloured cloak

upon the heath of Luchat in Dál Caiss.

Those are at all times in the west

the five prohibitions of the king of Cruachain.”

Kings were often the subject of numerous gessi , these reflected both his high status and also that his behaviour had a consequence for his people. Many of the gessi that governed the king’s actions don’t seem to make much practical sense. Here we see that the king must dress a certain way, approach from a certain direction, five prohibitions in total.  Then again there is so much in the interpretation that could be lost in the mists of time.

It is much more common to find people bound in more than one geis or gessi and this is when it becomes very perplexing, for sometimes one geis contradicted another. It was further complicated when the bearer did not know there were gessi placed upon them.

Diarmud for example was under a geis never to refuse to protect a woman; this gets him into hot water with his uncle, the mighty Fionn, when Grainne (Fionn’s wife) demands Diarmud protect her, and they of course fall in love.

Cuchulainn, who was bound in several came unstuck when he broke one of his.  One geis forbade him from eating dogmeat, while another forbade him the option of refusing food offered by a woman.  The Morrigan knew this, and disguised as hag offered him dog meat, he was forced to break one geis or the other, which eventually led to his death.

A geis, when placed upon the “hero” of the tale, creates a twin-fold bond. The geis can either bolster him in his quest (provided he remains stalwart and alert to the geis’ conditions), or by a disregard for the circumstances results in the hero’s death, or failure of his mission.

No reasons can be assigned for some gessi. If the geis were reasonable it was considered highly dishonourable to refuse it, irrespective altogether of the consequences. Some make sense on a practical level as statutory prohibitions of the strictest obligation and usually tied to one’s destiny. A geis foretold of an event that would need to pass before a person could be defeated and was often something that was considered beneficial, since unless you broke the geis, you were essentially invincible.