mid-13c., "harboring ill-will, enmity, or hostility," from Old French malicios "showing ill will, spiteful, wicked" (Modern French malicieux), from Latin malitiosus "wicked, malicious," from malitia "badness, ill will, spite," from malus "bad, unpleasant" (see mal-). In legal use (early 14c., Anglo-French), it means "characterized by malice prepense" (see malice).
Proto-Indo-European root meaning "false, bad, wrong." The exact sense of the root remains uncertain, "since it concerns a collection of largely isolated words in different IE branches" [de Vaan].
It forms all or part of: blame; blaspheme; blasphemous; blasphemy; dismal; mal-; malady; malaise; malaria; malediction; malefactor; malefic; malevolence; malevolent; malice; malicious; malign; malison; malversation; mauvais.
It is the hypothetical source of/evidence for its existence is provided by: Avestan mairiia‑, "treacherous;" Greek meleos "idle; unhappy;" Latin male (adv.) "badly," malus (adj.) "bad, evil;" Old Irish mell "destruction;" Armenian mel "sin;" Lithuanian melas "lie," Latvian malds "mistake," possbily also Greek blasphemein "to slander."
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.
Old English gefea, gefa "foe, enemy, adversary in a blood feud" (the prefix denotes "mutuality"), from adjective fah "at feud, hostile," also "guilty, criminal," from Proto-Germanic *faihaz (source also of Old High German fehan "to hate," Gothic faih "deception"), perhaps from the same PIE source that yielded Sanskrit pisunah "malicious," picacah "demon;" Lithuanian piktas "wicked, angry," peikti "to blame." Weaker sense of "adversary" is first recorded c. 1600.
"malicious burning of property," 1670s, from Anglo-French arsoun (late 13c.), Old French arsion, from Late Latin arsionem (nominative arsio) "a burning," noun of action from past participle stem of Latin ardere "to burn," from PIE root *as- "to burn, glow." The Old English term was bærnet, literally "burning;" and Coke has indictment of burning (1640).