Sibyl f. Ancient Greek Σίβυλλα 'sibyl'.
The name of a 12th C queen of Jerusalem, a 12th C queen consort of Scotland, a 13th C queen consort of Armenia, and a 13th C queen of Sicily.
The English diminutive Sib and the vernacular form Sibil are witnessed in 1379 in the relational bynames Sibsoñ (WRYPT1 p. 29), Sibsoñwif' (WRYPT1 p. 294), and Sibilsoñ (WRYPT1 p. 313).