"mitigating, soothing, alleviating," 1540s, from Latin mitigantem, present participle of mitigare (see mitigate). As a noun, "something that mitigates," by 1838.
miter
Mithras
mithridate
mithril
mitigable
mitigant
mitigate
mitigating
mitigation
mitochondria
mitochondrion