Probably of Persian origin; Sivan, the third Heb. Month -- Sivan.
H5510. Sivan
סִיוָן proper name of 3rd month, Siwan = May-June (loan-word from Assyrian -Babylonian Simânu, compare SchrCOT Nehemiah 1:1 Muss-ArnJRL xi (1892), 82 ff.; Palmyrene סיון Lzb328 Cook84); — ס הוּאתֹֿדֶשׁ הַשְּׁלִישֹׁי ׳בַּחֹדֶשׁ Esther 8:9.