Placate

google

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late 17th century: from Latin placat- ‘appeased’, from the verb placare .

wiktionary

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From Latin plācātus, past participle of plācō(“appease, placate”, literally “smooth, smoothen”), from Proto-Indo-European *plāk-(“smooth, flat”), from *pele-(“broad, flat, plain”). Related to Latin placeō(“appease”), Old English flōh(“flat stone, chip”). More at please.

etymonline

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placate (v.)

"appease or pacify," 1670s, a back-formation from placation or else from Latin placatus "soothed, quiet, gentle, calm, peaceful," past participle of placare "to calm, appease, quiet, soothe, assuage," causative of placere "to please" (see please). Related: Placated; placating; placatingly.