Edling (Welsh: etifedd) was a title given to the agreed successor or heir apparent of a reigning Welsh monarch. It is related to the English term Æþeling. While Æþeling or "noble child" (for example, see Edgar the Ætheling) was used in Anglo-Saxon England before the Norman Conquest to denote one of "royal blood", the Welsh use had a more precise meaning and denoted the acknowledged heir to the throne, usually the ruler's eldest son, although any son (legitimate or illegitimate) could be chosen as edling. In 1923, the academic T. H.
https://en.wikipedia.org/wiki/Edling