1590s, "act of doing or producing evil," from French maleficence or directly from Latin maleficentia "an evildoing, mischievousness, injury," from maleficus "wicked" (see malefic). Sense of "malefic character" is by 1796.

early 14c., "unfortunate, disastrous, miserably, wretchedly," probably from mischief + -ous. Sense of "playfully malicious or annoying" is attested by 1670s. "The stressing on the second syllable was common in literature till about 1700; it is now dialectal, vulgar, and jocular" [OED]. Related: Mischievously; mischievousness.