[1] Unattested as such elsewhere; and the manuscript variants reported by Adler (Sita, Sitia) are no help. There was a region called Sittakene, on the right bank of the Tigris, but its name seems to have derived from an unlocated city called Sit(t)ake (sigma 493), not Sitta. (A 'Sita Colonia' in Mauretania mentioned by George of Ravenna 3.8 is probably an error for 'Siga'.)
[2] Sittas was a Byzantine name. Probably the best-known bearer of it was the Armenian general and courtier prominent in the time of Justinian; cf. PLRE IIIb s.v. Sittas(1). He was the husband of Comitio (sister of the Empress Theodora) and father of Sophia (the Empress of Justin II). See Procopius, History of the Wars of Justinian 1.15 and passim.