Sorry, no definitions found. You may find more data at dallben.
Sorry, no etymologies found.
(link) I think I started having it a bit after I'd read enough genre fantasy to recognize things as tropes, instead of thinking of them in reference to "that one time Gandalf/Dallben/Merriman did X."
(Although I did have a moment of happy recognition when reading along in Kilhwch ac Olwen and finding in the list of Arthur’s men not only Fflewddur Fflam the blazing but also Dallben and Coll son of Collfrewr.