We don't have synonyms for assyrias yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are assyrian, assyrians and assyria.
(n) :
(historical) An ancient Semitic Akkadian kingdom and at times an empire, extant from the mid-23rd century BCE to 608 BCE and centred on the Upper Tigris river in northern Mesopotamia (present day northern Iraq, but at its maximum extent including parts of modern Iran, Syria, Israel, Palestine and Egypt).
(n) :
(historical) An ancient Semitic Akkadian kingdom and at times an empire, extant from the mid-23rd century BCE to 608 BCE and centred on the Upper Tigris river in northern Mesopotamia (present day northern Iraq, but at its maximum extent including parts of modern Iran, Syria, Israel, Palestine and Egypt).