The Sun Language Theory (Turkish: Güneş Dil Teorisi) was a Turkish nationalist pseudoscientific linguistic hypothesis developed in Turkey in the 1930s that proposed that all human languages are descendants of one proto-Turkic primal language. The theory proposed that because this primal language had close phonemic resemblances to Turkish, all other languages can essentially be traced back to Turkic roots. According to the theory, the Central Asian worshippers, who wanted to salute the omnipotence of the sun and its life-giving qualities, had done so by transforming their meaningless blabbering into a coherent set of ritual utterings, and language was born, hence the name.
Sun Language Theory Wikipedia
Influences on the theory included:the ideas of the French historian Hilaire de Barenton, expressed in "L'Origine des Langues, des Religions et des Peuples", that all languages originated from hieroglyphs and cuneiform used by Sumerians
a paper of the Austrian linguist Dr. Hermann F. Kvergić of Vienna entitled "La psychologie de quelques éléments des langues Turques" ("The Psychology of Some Elements of the Turkic Languages")
The founder and first president of the Republic of Turkey, Mustafa Kemal Atatürk, not only gave the theory official backing and material support but also was himself a very important contributor to its development, "though clearly he did not do all the donkey work".
As described in a 1936 New York Times article on the curriculum of the newly opened School of Language, History and Geography of Ankara University, the theory
claims that the Sumerians, being Turks, originating in Central Asia, all languages also consequently originated there and first used by the Turks. The first language, in fact, came into being in this way: Prehistoric man, i.e., Turks in the most primitive stage, was so struck by the effects of the sun on life that he made of it a deity whence sprang all good and evil. Thence came to him light, darkness, warmth and fire, with it were associated all ideas of time: height, distance, movement, size, and give expression to his feelings the sun was thus the first thing to which a name was given. It was "ag" (pronounced agh), and from this syllable all words in use today are derived. This, briefly, is the theory about the "sun language," and with the new conception of Turkish history it will be taught in the new Angora school.
In short, based upon a heliocentric view of the origin of civilization and human languages, the theory claimed that the Turkish language was the language which all civilized languages derived from.
Some of the words provided with false Turkish etymologies through the practice of goropism were school, which was attributed to the Turkish word okul (school); God, attributed to the Turkish kut (blessing); Bulletin from belleten (to learn by heart); Electric from Uyghur yaltrık (shine).
According to linguist Ghil'ad Zuckermann, "it is possible that the Sun Language Theory was adopted by Atatürk in order to legitimize the Arabic and Persian words which the Turkish language authorities did not manage to uproot. This move compensated for the failure to provide a neologism for every foreignism/loanword."