The paper focuses on the Old Polish word kryłos, which was attested twice in court records from Przemyśl in the 15th century. Some existing hypotheses about the word origin and meaning are mentioned, although it has not been discussed before in a satisfactory way. A detailed study of the word’s etymology (concerning Old Ukrainian, Old Russian and Greek) and a precise analysis of the attestations enables us to determine its meaning, different from the meaning proposed in the Dictionary of Old Polish ( Słownik staropolski).