The script is named after the Orkhon Valley in Mongolia where early 8th-century inscriptions were discovered in an 1889 expedition by Nikolai Yadrintsev. These Orkhon inscriptions were published by Vasily Radlov and deciphered by the Danish philologist Vilhelm Thomsen in 1893.
This writing system was later used within the Uyghur Khaganate. Additionally, a Yenisei variant is known from 9th-century Yenisei Kirghiz inscriptions, and it has likely cousins in the Talas Valley of Turkestan and the Old Hungarian alphabet of the 10th century. Words were usually written from right to left.
According to some sources, Orkhon script is derived from variants of the Aramaic alphabet, in particular via the Pahlavi and Sogdian alphabets, as suggested by Vilhelm Thomsen, or possibly via Kharosthi (cf. the inscription at Issyk kurgan).
Another explanation of the script's origin aside from derivation from tamgas, an alternate possible derivation from Chinese characters was suggested by Vilhelm Thomsen in 1893. Turkic inscriptions dating from earlier than the Orkhon inscriptions used about 150 symbols, which may suggest that tamgas first imitated Chinese script and then gradually was refined into an alphabet.
Thomsen (1893) connected the script to the reports of Chinese account (Records of the Grand Historian, vol. 110) from a 2nd century BCE Yan renegade and dignitary named Zhonghang Yue (Chinese: 中行说; pinyin: Zhōngháng Yuè), who "taught the Chanyu (rulers of the Xiongnu) to write official letters to the Chinese court on a wooden tablet (simplified Chinese: 牍; traditional Chinese: 牘; pinyin: dú) 31 cm long, and to use a seal and large-sized folder". The same sources tell that when the Xiongnu noted down something or transmitted a message, they made cuts on a piece of wood (gemu); they also mention a "Hu script". At the Noin-Ula burial site and other Hun burial sites in Mongolia and regions north of Lake Baikal, the artifacts displayed over twenty carved characters. Most of these characters are either identical with or very similar to the letters of the Turkic Orkhon script.