Where does “tranquillitas” come from?
tranquillitas (Latin) comes from Latin Tranquillus, from Latin trānsquīlus, from Latin quiēs, from Proto-Italic kʷiētis, from Proto-Indo-European kʷyéh₁tis, from Proto-Indo-European kʷyeh₁- — to rest; rest, peace.
Ancestry of “tranquillitas”, step by step