Old English cyningdom; see king (n.) + -dom. Cognate with Old Saxon kuningdom, Middle Dutch koninghdom, Old Norse konungdomr. The usual Old English word was cynedom; Middle English also had kingrick (for second element, see the first element in Reichstag). Meaning "one of the realms of nature" is from 1690s.
Kingdom-come (n.) "the next world, the hereafter" (1785), originally slang, is from the Lord's Prayer, where it is an archaic simple present subjunctive ("may Thy kingdom come") in reference to the spiritual reign of God or Christ.
Persian masc. proper name, in classical history a son of Xerxes II, also a son of Darius, from Greek Artaxerxes, from Old Persian Artaxšaca, literally "having a kingdom of justice," from arta- "justice" + xšaca "kingdom."
central European nation, from Medieval Latin Marchia austriaca "eastern borderland." German Österreich is "eastern kingdom," from Old High German ostar "eastern" (from Proto-Germanic *aust- "east," literally "toward the sunrise," from PIE root *aus- (1) "to shine," especially of the dawn) + reich "kingdom, realm, state" (from Proto-Germanic *rikja "rule," from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). So called for being on the eastern edge of Charlemagne's empire. Related: Austrian.