Indian summers reference American Indians, not the far east I believe.
The etymology of ‘Indian summer’
The expression ‘Indian summer’ has been used for more than two centuries. The earliest known use was by French-American writer St. John de Crevecoeur in rural New York in 1778. There are several theories as to its etymology:
In The Americans: The Colonial Experience, Daniel J. Boorstin speculates that the term originated from raids on European colonies by Indian war parties; these raids usually ended in autumn, hence the extension to summer-like weather in the fall as an Indian summer. Two of the three other known uses of the term in the 18th century are from accounts kept by two army officers leading retaliation expeditions against Indians for raids on settlers in Ohio and Indiana in 1790, and Pennsylvania in 1794.[2]
It may be so named because this was the traditional period during which early North American Indians harvested their crops of squash and corn.
In the same way that Indian giver was coined for people who take back presents they have bestowed, the phrase Indian summer may simply have been a way of saying “false summer. (However some traditions say “indian giver” refers to the practice of giving gifts at the end of pow wow to honor and support the receiver in living a good life.. If the recipient fails to do so, the giver may take back the gift.) “[3]
Similar usages in Europe
Saint Martin’s Summer by John Everett Millais
Altweibersommer in Germany
In former times in Europe, ‘Indian summer’ was called ‘Saint Martin’s Summer’, referring to St. Martin’s day, November 11, when it was supposed to end.
The phrase ‘Saint Martin’s Summer’ comes from France where it is still widely used. Saint Martin of Tours died in Candes sur Loire, now Candes-Saint-Martin, on November 8, 397 AD. His corpse was claimed by people of both Poitou and Touraine provinces. The latter pilfered him and brought him on a boat by the river Loire to Tours where he was and still is buried. Legend has it that the river banks flowered as his corpse went by from Candes to Tours.
In British English “St. Martin’s Summer” was the most widely used term until the American phrase Indian Summer became better known in the 20th century. In Italy, St Martin’s summer (Estate di San Martino) was expected and celebrated as a rural tradition with ancient origins, and is marked by a festival throughout the peninsula on November 11. In Spain, it is called Veranillo de San Miguel or Veranillo de San Martín, depending on which date it occurs (September 29 and November 11, respectively). It can also be called Veranillo del Membrillo (little summer of the quince). In Galicia (northern Spain), it is called Veraniño de San Martiño, and in Portugal it is called “Verão de São Martinho,” both of which refer to St. Martin’s summer. In both cases, it is celebrated in rural areas with Magostos (Magusto in Portuguese, from Magnus Ustus, Big Fire in reference to the magical nature of fire), a celebration of Celtic origins in which bonfires, roasted chestnuts and wine have an important role. Even in the eastern part of the Iberian Peninsula the catalans have its ‘Estiuet de Sant Martí although the climate is just the opposite to the galician one.
It is called Old Ladies’ Summer in Russia Babye Leto (????? ????), in Poland Babie Lato, in Ukraine Babyno Lito (?????? ????), in Czech Republic Babí léto, in Slovakia “Babie leto” and in Croatia Bablje ljeto. In Bulgaria, the phenomenon is sometimes called “Gypsy Summer” (Bulgarian: ???????? ????, tsigansko lyato) and in some places “Gypsy Christmas” and refers to unseasonably warm weather in late fall, or a warm spell in between cold periods.
In Sweden it is called “brittsommar”, which is derived from Birgitta and Britta, who have their “name day” in the Swedish calendar on October 7. That is when Britt Mass, an official fall open-air market, was held.
In Germany and Austria it is called “Altweibersommer”, in Hungary “vénasszonyok nyara” (Old Ladies’ Summer or Crone’s Summer) because the many white spiders seen at this time of the year have been associated with the norns of Norse folklore or medieval witches. In Flanders (Belgium) it is also called “Oudewijvenzomer” (Old Ladies’ Summer) or “Trezekeszomer” (“St-Theresa’s Summer — St-Theresa’s Day being on 15 October).
In Welsh, it is known as “Haf Bach Mihangel” or (St.) Michael’s Little Summer – St. Michael’s Day being on 29 September.
An alternative to St Martin’s summer was “Saint Luke’s summer”, as the saint’s feast day is October 18. Another alternative was “All-hallown summer”, as Halloween is October 31; the expression is used in Shakespeare’s King Henry IV, Part 1, Act 1 Scene 2.
In Lithuania this time is called “Bob? vasara”, which translates to “summer of old ladies”.
In Latvia this period is called “Atvasara”, which translates to “re-summer” or “return/repeat/flashback of summer”.
In Turkey the term “past?rma yaz?”, meaning Pastrami Summer is used.