foretale

An account or telling given as an introduction to a larger body of work; prologue; a prior or previous recollection or account of events

The first three paragraphs of the translation are a condensed paraphrase of the first foretale, which tells of the birth of Aengus and how he obtains Etain for Midir by clearing twelve plains and creating twelve rivers (only nine are named in the story) [...]

Mentioned in the ancient lists as Prime Stories, these short narratives were evidently foretales (remscéla) to the saga of Conaire Mor, the Great King of Tara, regarded by several clans as their ancestor.

An account given in advance; prediction

One can gain further insight by looking at what “foretales/ prophecies” are, and how they are made. It is interesting to consider the very terms themselves, and their evolution through time.