constellation (n.) Look up constellation at
early 14c., constellacioun, "position of a planet in the zodiac;" late 14c., "one of the recognized star patterns handed down from antiquity" (in the zodiac or not), from Old French constellacion "constellation, conjuncture (of planets)," from Late Latin constellationem (nominative constellatio) "set with stars," from constellatus, from Latin com "with, together" (see com-) + past participle of stellare "to shine," from stella "star" (see star).

The oldest sense is astrological, of the position of planets ("stars") relative to the constellations on a given day, usually the day of one's birth, as a determiner of one's character. "I folwed ay myn inclinacioun/By vertu of my constillacioun" (Chaucer, "Wife's Prologue," c. 1386).

The classical northern constellations probably were formed in prehistoric Mesopotamia; the Greeks likely picked them up c. 500 B.C.E., and Claudius Ptolemy (c. 90-c. 168) of Alexandria codified 48 of them, all still current, in his "Almagest" (2c.). The canonical list was expanded from 16c. as Europeans explored southern regions whose stars were invisible from Alexandria and as astronomers filled in the dimmer regions between the established figures, so that by the late 19c. as many as 109 constellations were shown on maps. The modern roster was set at 88 by the International Astronomical Union in 1922.