named and/or invented since the late 15th century, when "civilization" began spreading from Europe/the Middle East and discovering new stars and star patterns not accounted for in their tradition (paying no heed, of course, to those previously unknown astrological/astronomical traditions they did come across and wipe their feet on...)
While this was underway, a few clusters of stars in familiar but previously-unlabelled space were also given names just to make the contents of the sky as full and "complete" as possible. Modern constellations frequently lack the mythic qualities or even inspiration shown by the original constellations. Compare: the snake-bearer to the triangle. See whut I mean, Vern?