real (adj.)youdaoicibaDictYouDict
early 14c., "actually existing, true;" mid-15c., "relating to things" (especially property), from Old French reel "real, actual," from Late Latin realis "actual," in Medieval Latin "belonging to the thing itself," from Latin res "matter, thing," of uncertain origin. Meaning "genuine" is recorded from 1550s; sense of "unaffected, no-nonsense" is from 1847.
Generally, by the time you are Real, most of your hair has been loved off, and your eyes drop out and you get loose in the joints and very shabby. But these things don't matter at all, because once you are Real you can't be ugly, except to people who don't understand. [Margery Williams, "The Velveteen Rabbit"]
Real estate, the exact term, is first recorded 1660s, but in Middle English real was used in law in reference to immovable property, paired with, and distinguished from, personal. Noun phrase real time is early 19c. as a term in logic and philosophy, 1953 as an adjectival phrase; get real, usually an interjection, was U.S. college slang in 1960s, reached wide popularity c. 1987.
sidereal (adj.)youdaoicibaDictYouDict
also siderial, 1630s, "star-like;" 1640s, "of or pertaining to the stars," earlier sideral (1590s), from French sidereal (16c.), from Latin sidereus "starry, astral, of the constellations," from sidus (genitive sideris) "star, group of stars, constellation," probably from PIE root *sweid- "to shine" (cognates: Lithuanian svidus "shining, bright"). Sidereal time is measured by the apparent diurnal motion of the fixed stars. The sidereal day begins and ends with the passage of the vernal equinox over the meridian and is about four minutes shorter than the solar day, measured by the passage of the sun over the meridian.