WordNet sense 1 (the act of appeasing (as by acceding to the demands of)):

appeasement

WordNet sense 2 (freeing from fear and anxiety):

soothing, assuasive, pacifying

WordNet sense 3 (restoring confidence and relieving anxiety):

reassuring

WordNet sense 4 (causing to become tranquil):

lulling, quietening

WordNet sense 5 (not alarming; assuaging alarm):

unalarming