to lessen the unpleasantness of (e.g. a disease) without removing the cause
to disguise the gravity of (a fault or offence) by excuses or apologies
to moderate the intensity or gravity of (something)
palliation /-ʹaysh(ə)n/ noun
palliator noun
[late Latin palliatus, past part. of palliare to cloak, conceal, from pallium cloak]