Mythbusting - Diarmuid’s Love Spot
Despite being an integral part of many depictions of Diarmuid (including, possibly most famously, the Fate series), there’s actually nothing in the world of medieval or early modern Irish literature to indicate that Diarmuid (”Diarmaid” in the Old Irish) had a love spot. That account comes from later folklore that was written down.
Which doesn’t mean that the story is fake -- rather that it’s a development of a living oral tradition, as opposed to the oldest accounts of the story that we know. Which in itself is a rather late addition -- In Acallam na Senorach (12th-13th century), for example, Diarmaid’s death by boar is mentioned for the first time, but there’s no hint of Gráinne or Fionn’s jealousy. And there’s one very interesting story from about the 11th century or so that has Fionn and Gráinne marrying.....and then promptly divorcing peacefully when he realizes that she hates him.
There are a few traditions about a lover of Fionn’s betraying him with one of his men, but not anything like we’d associate with Diarmaid and Gráinne, at least in the early, Old Irish materials. The oldest manuscript we have that contains the whole story is from 1651; we have a few manuscripts that date to the 18th and 19th centuries, and that account is believed to date to around the 14th century. Which seems REALLY old until you remember that some of the other Fenian material dates to the 8th century, over six hundred years before that.
Just to hammer this home: There is LESS time between us and Shakespeare than there is between when the earliest Fenian Cycle material shows up and the first extended surviving Diarmuid and Gráinne narrative shows up. A rough equivalent would be the difference in time between the Canterbury Tales and Harry Potter. Or between us now and when La Morte d’Arthur was written. Obviously, it doesn’t mean that there was NOTHING about them circulating at the time (we know that there was one that was circulating in the 10th century), but it means that it wasn’t written down or, in the case of the 10th century one, lost.