Perhaps borrowed from Doric Greekμᾶλον(mâlon, “apple”). Alternatively but less likely from Proto-Indo-European*méh₂lom. The Proto-Indo-European word in fact regularly give both mālum in Latin and μῆλον in Ancient Greek, but such reconstruction is dubious due to the fact that it is only found in some Indo-European languages. It is more likely that the Greek word was borrowed from a pre-Indo-European subratum and later borrowed into Latin. See μῆλον for more details.
malum in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
malum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
Carl Meißner, Henry William Auden (1894) Latin Phrase-Book, London:Macmillan and Co.
(ambiguous) to be broken down by misfortune: in malis iacere
(ambiguous) to be hard pressed by misfortune: malis urgeri
(ambiguous) to deserve ill of a person; to treat badly: male mereri de aliquo
(ambiguous) to have a good or bad reputation, be spoken well, ill of: bene, male audire (ab aliquo)
(ambiguous) to have a good or bad reputation, be spoken well, ill of: bona, mala existimatio est de aliquo
(ambiguous) to inculcate good (bad) principles: bene (male) praecipere alicui
(ambiguous) moral science; ethics: philosophia, in qua de bonis rebus et malis, deque hominum vita et moribus disputatur
(ambiguous) my mind forebodes misfortune: animus praesāgit malum
(ambiguous) my mind forebodes misfortune: animo praesagio malum
(ambiguous) a guilty conscience: conscientia mala or peccatorum, culpae, sceleris, delicti
(ambiguous) a guilty conscience: animus male sibi conscius
(ambiguous) to be tormented by remorse: conscientia mala angi, excruciari
(ambiguous) a moral (immoral) man: homo bene (male) moratus
(ambiguous) to bless (curse) a person: precari alicui bene (male) or omnia bona (mala), salutem
(ambiguous) to manage one's affairs, household, property well or ill: rem bene (male) gerere (vid. sect. XVI. 10a)
(ambiguous) from beginning to end: ab ovo usque ad mala (proverb.)
(ambiguous) to buy dearly: magno or male emere
(ambiguous) to win, lose a fight (of the commander): rem (bene, male) gerere (vid. sect. XII. 2, note rem gerere...)
(ambiguous) I am sorry to hear..: male (opp. bene) narras (de)