Where does “levirate” come from?

I need to work through this etymology chain carefully. The chain given is: English -ate | Latin -atus | Proto-Indo-European dayh₂wḗr | Proto-Italic -ātos | Proto-Indo-European -tós | Proto-Indo-European -tós This appears problematic - it mixes what seems to be a root (dayh₂wḗr) with suffixes, and ends with -tós twice. However, I must work with what's given and state only what the chain supports. Looking at "levirate" - this actually relates to the Latin "levir" (brother-in-law) + the suffix -ate. The chain seems malformed for this word, but I must follow the instruction to use only what the chain supports. The most honest approach given the confused chain: I should note that the chain as presented doesn't clearly support the etymology of "

levirate (English): Having to do with one's husband's brother; A...