Where does “expiational” come from?

expiational (English) comes from English expiation, from Middle French expiation, from Latin expiatio, from Latin -tiō, from Latin dissertātiō, from Latin dissertus, from Latin disserere, from Latin dis- — small stone, pebble; gravel, rubble.

Ancestry of “expiational”, step by step

expiational traces back through two separate lines of ancestry.

via English expiation

StepLanguageWordMeaning
1EnglishexpiationAn act of atonement for a sin or wrongdoing; The...
2Middle Frenchexpiation
3Latinexpiatiosatisfaction, atonement, expiation, purification
4Latin-tiōtion, -ation, -ing
5Latindissertātiō(spoken) dissertation, discourse, disquisition
6Latindissertusarranged, disposed; explained
7Latindissereresecond-person singular future passive indicative...
8Latindis-asunder, apart, in two; reversal, removal;...
9Latincalceusshoe
10Latincalxlimestone; chalk; the finish line
11Ancient Greekχάλιξsmall stone, pebble; gravel, rubble

via English AL

StepLanguageWordMeaning
1EnglishALInitialism of assembly language; Initialism of...
2Dutchalall, all of; already; yet
3Middle Dutchalall, all of; completely; even though, no matter...
4Old Dutchāl
5Proto-West Germanicallall
6Proto-Germanicallazall
7Proto-Indo-Europeanh₂él-to grow, nourish
Every word from Ancient Greek χάλιξEvery word from Latin -tiōEvery word from Latin dis-