CECIL. The name of this noble family was written in ancient times, Sitailt, Sicelt, Seycil, Seisil, Cyssell, kc, until William Cecil, Lord Burghley, Queen Elizabeth's famous minister, from a whimsical notion that he was descended fi'om the Roman Cascilii, adopted the present orthography. The iiimily, doubtless of Norman origin, can be traced to Roliert Sitsilt, M'ho in 1091 assisted Robt. Fitz-Hamon in the conquest of Glamorganshire. Collins.

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.