The more common Middle English form was Ynde or Inde, from Old French (hence Indies). The form India began to prevail again in English from 16c., perhaps under Spanish or Portuguese influence.
It is the American version of British All-Hallows summer, French été de la Saint-Martin (feast day Nov. 11), etc. Also colloquial was St. Luke's summer (or little summer), period of warm weather occurring about St. Luke's day (Oct. 18). An older and simpler name for it was autumn-spring (1630s).
river in Asia, from Sanskrit sindhu "river." The constellation was one of the 11 added to Ptolemy's list in the 1610s by Flemish cartographer Petrus Plancius (1552-1622) after Europeans began to explore the Southern Hemisphere; it represents "an Indian," not the river.