has reversed its original meaning (Latin, demereo, to merit, to deserve). Hence Plautus, Demertas dare laudas (to accord due praise); Ovid, Numina culta demeruisse; Livy, dernerèri beneficio civitatem. The de—is intensive, as in “de-mand,” “de-scribe,” “de-claim,” etc.; not the privative deorsum, as in the word “de-fame.”
My demerits [deserts] May speak unbonneted.
Shakespeare: Othello, i. 2.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894