From Proto-Italic *kʷjētis, from Proto-Indo-European *kʷyéh₁-ti-s, from *kʷyeh₁- (“to rest”).
Cognates include Avestan 𐬱𐬁𐬌𐬙𐬌- (šāⁱti-, “happiness”), Old Persian [script needed] (šiyāti-, “luck”), Old Armenian հանգչիմ (hangčʻim). See also tranquillus.