Where does “tranquillissimo” come from?

tranquillissimo (Italian) comes from Italian tranquillo, 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 “tranquillissimo”, step by step

StepLanguageWordMeaning
1Italiantranquillocalm, sober, tranquil
2LatinTranquillusquiet, calm, still, tranquil
3Latintrānsquīlus—
4Latinquiēsthe rest of sleep, repose
5Proto-Italickʷiētis—
6Proto-Indo-Europeankʷyéh₁tis—
7Proto-Indo-Europeankʷyeh₁-to rest; rest, peace
Every word from Proto-Indo-European kʷyeh₁- →Every word from Proto-Indo-European kʷyéh₁tis →Every word from Proto-Italic kʷiētis →