Known also as the »Pangs of Ulster« or ces noinden, »ninefold affliction«, this is the strange and indeterminate ailment suffered by the men of Ulster which prevents them from going to war in the Táin Bó Cúailnge. Although modern collections of myths and stories like to make it very clear in its origin and effects, this is not at all borne out by the sources, and it is in fact a difficult and mysterious problem. For one thing, noinden, ninefold, is generally expanded to »nine days'«, but this makes little sense, since the Ulstermen lie in their debility for several months in the Táin while Cú Chulainn defends them alone. For another, Cú Chulainn is said to be spared from the pangs because he is not of the Ulaid; although he belongs to the tribe by adoption, affiliation, and blood on his mother's side, his father Súaltaim is an outsider. So far, so good; the debility is hereditary on the patriline, we can assume — but then Súaltaim is himself the brother of Fergus mac Róich, the king of Ulaid preceding Conchobar mac Ness, so how does that fit together? Third, although »pangs« is conventional, even the form or symptoms are not actually clear — one or two places in Recension 1 of the Táin seem to imply that the debility is in fact an enchanted sleep, not an immobilizing pain. A fourth difficulty arises from the fact that the Ulstermen in exile, led by the same Fergus and participating on the side of Connacht in the cattle raid, are also apparently untouched by the affliction; a fifth is the unclear and conflicting accounts of the origins of the illness. There are to my knowledge at least two competing stories of this origin preserved in the manuscripts:
Ces Noinden Ulad
This story, which we may class as the first, involves a farmer boasting of the speed of his wife Macha, who is forced to race a chariot as a result, despite being pregnant; she wins the race but dies and curses the men of Ulaid to suffer the pangs of childbirth, either one day for each month of pregnancy, or for five days and four nights unto the ninth generation (neither of which, it will be noted again, is actually how it works in the main story). This is the version preferred by modern lay editors, especially the wiccan hippie kind, who also insist on referring to the wife as »the goddess Macha« even though most likely the woman is only given this name for onomastic purposes: as she dies, she gives birth to twins, thus also giving Emain Macha its name, which literally means »The Twins of Macha«; this onomastic is blatantly false, with the likely real origin being that two hills were called »the Twins of Macha« in the same way that two other hills elsewhere in Ireland have been called »the Paps of Anu« — that is, the earth goddess' breasts. The wife Macha is given the name of the goddess Macha simply to enable the substitution, not because one is the avatar of the other, because they are two aspects of a tripartite goddess, or some other convoluted foofaraw that fails every reasonable test of simplicity.
While common and complete in the sources — it appears in the Yellow Book of Lecan, the Book of Leinster, and the Book of Fermoy among others — this story is not in fact very satisfactory, because it bears all the hallmarks of an ex post facto product, intended to explain and justify a number of things whose proper explanations had been forgotten; from memory, it is not preserved in any Old Irish version, only a Middle Irish one first written down at some point during the 12th century.
Ces Ulad
This is the second story, which it will be noted has a confusingly similar name. It is far less well attested, existing only in one manuscript (an obscure one in the British Library designated MS Harleian 5280; unlike the abovementioned codices it has no conventional name), and preserved there only in a fragmentary form, but also apparently older; in this story, the seeress Fedelm, who also appears in the Táin proper, encounters Cú Chulainn at a ford with the consequence that she promises to be his concubine for a year and a day and also to display herself naked before all Ulaid; when she fulfils this latter promise, the product is the debility.
Here presumably the idea is that since both of these things shame her, and she also has profound magical powers, she inflicts the torments of being shamed on the Ulaid (the motif of shame having physical consequences was perfectly established and recurrent in Old Irish literature, another prominent example being Senchán Torpéist satirizing a king so hard he breaks out in big red boils and blisters all over his body), which does permit a neat resolution to the problem of the exiles and Súaltaim — they are simply not present — but in return, makes it particularly hard to understand how Cú Chulainn, who is the primary instigator, would be specifically spared. We can construct theories to the effect that it is precisely because Cú Chulainn is the cause of this shame that he is immune to it, but here again we are entering dangerous waters since there is no explicit support whatever of such a causation within the story itself; in other words we have embarked on precisely the type of pure confabulation which is one of the greatest threats to accurate analysis. In any case, this story, too, is unsatisfactory, both insofar as it is incomplete (the preserved portion is actually significantly shorter in full than this paragraph discussing it) and insofar as it explains nothing about the ces except its origin, which does little to clear up any of the other problems; but then again, it does also avoid giving answers which are obviously wrong.
So much for these attempts. I will state frankly that for all its difficulties, I myself prefer the second story as things stand; not only does it fit better with the Táin itself, it also fits the word ces better, which is nowhere else associated with the pain of childbirth, but is theorized to have originally meant »hibernation«, as per the hypothesis mentioned above of an enchanted sleep. There is also the general rule of thumb for Irish literature that the more fragmentary, the harder to understand and the more terse a given tale is, the older it is likely to be, which points strongly in favor of Ces Ulad.
Of course, it will have been observed from the start by the perceptive reader that the actual cause and function of the debility is as a narrative convenience — to provide an excuse for Cú Chulainn to fight alone against the host of the invaders; and this is naturally true. Seeking a justification within the plot for each convolution and discrepancy is ultimately futile, in that the fundamental justification is external; literature is not physics, and there is no law bending all things to fit seamlessly together, least of all within the oral literature of the ancestors, kept only in living minds and not on inert paper. We are obliged to admit that in spite of the preoccupation of the ancient Irish poets with connection and cohesion within the Ulster Cycle, and in spite of the existence of two separate explanatory stories — which shows that the problem was both known and a point of concern to the poets — we do not have such a solution, or even the indication that there ever was one. Ultimately, we must be satisfied with merely indicating the difficulty, without succumbing to the temptation to patch and fix. This is not unusual when treating with ancient literature; overinterpretation and sheer invention are two of the most common pitfalls of amateurs and bunglers.