This name is frequently written Pactlus, but in inscriptions we only find Paccius, and the derivative Pacciauus also points to Paccius as the correct orthography. It appears that the name was originally not Roman. [See Nos. 1 and 2.]
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