1560s, "state or quality of being legally null and void," from French nullité (14c.) or directly from Medieval Latin nullitalis, from Latin nullus "not any" (see null). From 1580s as "a state of nothingness;" in reference to persons, "a non-entity," by 1650s.

the modern English word is a merger of two words, both in Middle English as quashen, from two unrelated Latin verbs.

1. "to suppress, overcome" (mid-13c.); "to make void, annul, nullify, veto" (mid-14c.), from Old French quasser, quassier, casser "to annul, declare void," and directly from Medieval Latin quassare, alteration of Late Latin cassare, from cassus "null, void, empty" (from extended form of PIE root *kes- "to cut"). The meaning "subdue, put down summarily" is from c. 1600.

2. "to break, crush, beat to pieces" early 14c., from Old French quasser, casser "to break, smash, destroy; maltreat, injure, harm, weaken," from Latin quassare "to shatter, shake or toss violently," frequentative of quatere (past participle quassus) "to shake," from PIE root *kwet- "to shake" (source also of Greek passein "to sprinkle," Lithuanian kutėti "to shake up," Old Saxon skuddian "to move violently," German schütteln "to shake," Old English scudan "to hasten").

In Medieval Latin, quassare often was used for cassare, and in later French the form of both words is casser. The words in English now are somewhat, or entirely, fused. Related: Quashed; quashing.

in medicine, "exhaustion from lack of nourishment," c. 1400, "pathological draining or depletion of blood, humors, or bodily fluids," from Old French inanition (14c.) and directly from Latin inanitionem (nominative inanitio) "emptiness," noun of action from past-participle stem of inanire "to empty," from inanis "empty, void; worthless, useless," a word of uncertain origin.

1570s, "to purify, clarify, clear from dregs or impurities," from Latin defaecatus, past participle of defaecare "cleanse from dregs, purify," from the phrase de faece "from dregs" (see de- + feces). Figurative sense "purge of extraneous matter" is from 1620s. Excretory sense "void feces from the bowels" is by 1849 in medical writing, probably from French. Related: Defecated; defecating.

early 15c., "a condition on performance of which a deed is rendered void," from Anglo-French defesaunce, Old French desfaisance "undoing, destruction," from desfaire (Modern French défaire) "to undo, destroy," from Vulgar Latin *diffacere "undo, destroy," from Latin dis- "un-, not" (see dis-) + facere "to do, perform," from PIE root *dhe- "to set, put." Related: Defease; defeasible.