1560s, "to bring (a building) to ruin, bring into a ruinous condition by misuse or neglect," from Latin dilapidatus, past participle of dilapidare "to squander, waste," originally "to throw stones, scatter like stones," from dis- "asunder" (see dis-) + lapidare "throw stones at," from lapis (genitive lapidis) "stone" (see lapideous). Perhaps the English word is a back-formation from dilapidation. Intransitive sense of "fall into total or partial ruin" is from 1712.
mid-14c., omissioun, "a neglect or failure to do what one has power to do or ought to do," from Anglo-French omission (early 14c.), Old French omission and directly from Late Latin omissionem (nominative omissio) "an omitting," noun of action from past-participle stem of Latin omittere "disregard," literally "let go, let fall" (see omit). Meaning "act of leaving out" is from 1550s. Related: Omissible.
1590s, "abandonment, state of being forsaken or abandoned" (formerly with a wider range than in modern use, such as of the sea withdrawing from the land), from Latin derelictionem (nominative derelictio) "an abandoning; a disregarding, neglecting," noun of action from past-participle stem of derelinquere (see derelict).
Sense of "act of leaving with an intention not to reclaim or reuse" is from 1610s. Meaning "failure, unfaithfulness, neglect" (with regard to duty, etc.) is by 1778. Phrase dereliction of duty attested from 1776.
"In the 16th and 17th centuries frequently used as a term of general disparagement" [OED]. In plant an animal names, "having the color of rust." Of bodily skills, "impaired by neglect," from c. 1500; extended to mental qualities, learning, skills, accomplishments, etc., by 1796. Related: Rustily; rustiness.
mid-15c., dilapidacioun, "wasteful expenditure, squandering;" late 15c., "state of disrepair, gradual ruin or decay, especially through misuse or neglect," from Late Latin dilapidationem (nominative dilapidatio) "a squandering," noun of action from past-participle stem of Latin dilapidare "throw away, squander, waste," probably etymologically "scatter like stones," from dis- "asunder" (see dis-) + lapidare "throw stones at," from lapis (genitive lapidis) "stone" (see lapideous). "Taken in Eng. in a more literal sense than was usual in Latin" [OED].
Old English forgietan "lose the power of recalling to the mind; fail to remember; neglect inadvertently," from for-, used here probably with privative force, "away, amiss, opposite" + gietan "to grasp" (see get (v.)). To "un-get," hence "to lose" from the mind. A common Germanic construction (compare Old Saxon fargetan, Old Frisian forjeta, Dutch vergeten, Old High German firgezzan, German vergessen "to forget"). The physical sense would be "to lose (one's) grip on," but that is not recorded in any historical Germanic language. Figurative sense of "lose care for" is from late 13c. Related: Forgetting; forgot; forgotten.
It forms all or part of: amblyopia; bland; blandish; blenny; emollient; enamel; malacia; malaxation; malt; melt; mild; Mildred; milt; moil; mollify; Mollusca; mollusk; mulch; mullein; mutton; schmaltz; smelt (v.); smelt (n.).
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit mrdh "to neglect," also "to be moist;" Greek malakos "soft," malthon "weakling;" Latin mollire "soften," mollis "soft;" Old Irish meldach "tender."
"writ from a superior court to an inferior court or officer specifying that something be done by the persons addressed, as being within their office or duty," 1530s (late 14c. in Anglo-French), from Latin mandamus "we order" (opening word of the writ), first person plural present indicative of mandare "to order" (see mandate (n.)). "Its use is generally confined to cases of complaint by some person having an interest in the performance of a public duty, when effectual relief against its neglect cannot be had in the course of an ordinary action" [Century Dictionary].