Where does “spietatissimo” come from?

spietatissimo (Italian) comes from Italian spietato, from Italian pietà, from Latin pietas, from Latin pīus, from Latin -tās, from Proto-Indo-European -teh₂ts, from Proto-Indo-European -teh₂, from Proto-Indo-European -tós — Creates verbal adjectives from verb stems.

Ancestry of “spietatissimo”, step by step

StepLanguageWordMeaning
1Italianspietatomerciless, ruthless, pitiless, cruel
2Italianpietàpity, compassion, godliness; piety; pietà
3LatinpietasDutiful conduct, sense of duty; Piety,...
4Latinpīus
5Latin-tāsty, -dom, -hood, -ness, -ship
6Proto-Indo-European-teh₂tsUsed to form nouns representing state of being
7Proto-Indo-European-teh₂Used to form nouns representing state of being
8Proto-Indo-European-tósCreates verbal adjectives from verb stems
Every word from Proto-Indo-European -tós