Origin: 1375–1425; late Middle English mitigaten < Latin mītigātus (past participle of mītigāre to calm, soften, soothe), equivalent to mīt(is) mild, soft, gentle + -ig- (combining form of agere to do, cause to do, make) + -ātus-ate1
Can be confused:militate, mitigate (see usage note at the current entry).
Usage note Mitigate, whose central meaning is “to lessen” or “make less severe,” is sometimes confused with militate, “to have effect or influence,” in the phrase mitigate against: This criticism in no way militates (not mitigates) against your going ahead with your research. Although this use of mitigate occasionally occurs in edited writing, it is rare and is widely regarded as an error.
early 15c., from L. mitigatus, pp. of mitigare "make mild or gentle," ultimately from mitis "gentle, soft" + root of agere "do, make, act" (see act). First element is from PIE base *mei- "soft, mild." Related: Mitigated; mitigates.