I thought about having a look to see if there were any correspondences between the Lay of Iubhdan and the Auraicept and bríatharogam kennings. At this stage there doesn’t seem to be a lot of correspondence; some don’t seem to be connected at all and some require a very great stretch of imagination. Nevertheless, three did seem to have a degree of correspondence that was quite striking.
The Lay mentions the “battle-witch of woods” that is “hottest in the fight” with a warning to burn it at discretion. In the bríatharogam we find alder as the “vanguard of warriors” (Bríatharogam Morann mic Moín).
The similarity here was quite striking. The Lay mentions the bees sucking nectar within the willow’s blooms and in the kennings we find willow as the “sustenance of bees” (Bríatharogam Mac ind Óc) and the “beginning of honey” (Bríatharogam Con Culain).
The Auraicept indicates furze, but this seems unlikely given the attributes, so I have preferred the usual interpretation of ash. The Lay mentions ash as the timber that makes the wheels go around and also mentions mounted horsemen and warriors. The respective bríatharogam kennings are “wounder of horses”, “smoothest of craftsmanship” and “equipment of warriors” – suggesting a connection with warriors and cavalry. Of course, ash is a strong wood, good for an axle, a hurling stick or a spear.
A lot more research needs to be done, and perhaps it already has been, but I would say that it is certainly tempting to see some of these attributes as originating in a common culture and poetic heritage. Of course, two entirely different poets stating the obvious, such as some wood or other is good for its usual use, does not a correspondence make, however, some of these seem to be a little deeper than that.