Where does “tranquillite” come from?
tranquillite (Middle English) comes from Old French tranquillite, from Latin tranquillitās, 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 “tranquillite”, step by step