From Old Turkic𐱅𐰭𐰼𐰃(teŋri, “god of the blue sky”), from Proto-Turkic*teŋri or *taŋrɨ(“god; sky, heaven”), which, according to the controversial Altaic hypothesis, is possibly from Proto-Altaic*t`aŋgiri(“oath, God”). According to G. Starostin's interpretation this word is based in a common Altaic religious or juridical term. This proposed etymology presumes that 'sky' in Turkic has a secondary meaning being derived from the primary meaning 'God'. S. Georg proposed a loan in Turkic from Yenisseian *tɨŋgVr- 'high' (see Georg 2001).
The Old Turkic form is recorded by Mahmud al-Kashgari (11th century). The oldest form of the name is recorded in Chinese annals from the 4th century BC, describing the beliefs of the Xiongnu. It takes the form 撐犁／撑犁 (chēnglí), which is understood as a Chinese transcription of the Proto-Turkic form.
The further origin of the word is uncertain. Also compare Proto-Turkic *teŋiŕ (cf. Turkish deniz(“lake, sea”) and the borrowing into Hungarian tenger); perhaps from the blue expanse.