the name of several Roman families, appears to be merely a lengthened form of Silus, which occurs as a cognomen in the Sergia and Terentia gentes [SILUS], and is not connected with the Greek name Silanus. Instead of the Roman name Silanus we frequently find in manuscripts Syllanus and Sillanus.
A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890