The author of this article conclusively traces the source of the two Aesopic fables retold in the prologue to Adonias saga to the medieval collection of Latin fables known as Anonymus Neveleti (alias Romulus elegiacus), fragments of which are preserved in two Icelandic vellum bifolia (Þjms frag 103 and 104) that probably originate from the Benedictines monastic houses of North Iceland. In a review of various ancient and medieval collections of Aesop’s fables, the author concludes that the unknown Icelandic author of Adonias saga must have been familiar with the two fables in this particular Latin version, even though his Icelandic rendering of them is free and likely based on memory. A parallel to a Latin couplet cited in the prologue is furthermore identified in a bilingual encyclopædic manuscript, AM 732 b 4to, also associated with the northern Benedictines. The author of the article suggests the possibility that the incorporation of two Aesopic fables in the prologue to Adonias saga, a riddarasaga, is an indication that such sagas ought to be interpreted like fables, that is not only read as entertainment but also as ethical instruction.