<P> Late - 19th century Boston lexicographer Albert Matthews made an exhaustive search of early American literature in an attempt to discover who coined the expression . The earliest reference he found dated from 1851 . He also found the phrase in a letter written in England in 1778, but discounted that as a coincidental use of the phrase . </P> <P> Later research showed that the earliest known reference to Indian Summer in its current sense occurs in an essay written in the United States in the late 1770s (probably 1778) by J. Hector St. John de Crevecoeur . The letter was first published in French . The essay remained unavailable in the United States until the 1920s . </P> <P> Although the exact origins of the term are uncertain, it was perhaps so - called because it was first noted in regions inhabited by Native Americans ("Indians"), or because the Native Americans first described it to Europeans, or it had been based on the warm and hazy conditions in autumn when Native Americans hunted . </P> <P> In literature and history, the term is sometimes used metaphorically . The title of Van Wyck Brooks' New England: Indian Summer (1940) suggests an era of inconsistency, infertility, and depleted capabilities, a period of seemingly robust strength that is only an imitation of an earlier season of actual strength . William Dean Howells' 1886 novel "Indian Summer" uses the term to mean a time when one may recover some of the happiness of youth . The main character, jilted as a young man, leads a solitary life until he rediscovers romance in early middle age . </P>

Where did the expression luke warm come from