No

This form of our "negative reply" dates to the early 13th century from the Old English adverb na ("never, "), which came from ne + a ("not, no" + "ever"). Both combined forms ultimately derive from Proto-Indo-European: ne from *ne- ("no, not") and a from *aiw- ("vital force, life, long life, eternity"). *Aiw- is also the forebear of aye ("assent"). The adjective no meaning "not any" dates to the 1200's and comes from Old English nan, the forebear of none.

As English speakers, yes and no are a basic and fundamental part of language. Actually, in every language the ability to express agreement and disagreement are basic and fundamental, but not every system is as simplistic as ours. Chinese, for example, doesn't really have a word for yes and no word for no. Instead, speakers echo the question with their answer. For example: Shi bu shi? asks "Is it?", the answer is either Shi ("It is") or Bu shi ("It isn't"). It is also possible for a language to have multiple versions of yes and no that are used in different contexts. In Middle English yea, nay, yes, and no were all used. Yea and nay answered questions that were framed positively ("Are you coming?") while yes and no answered negatively framed questions ("Are you not coming?").

Avoirdupois

Avoirdupois \av-uhr-duh-POIZ\ or \AV-uhr-duh-poiz\ , noun;
1. Avoirdupois weight, a system of weights based on a pound containing 16 ounces or 7,000 grains (453.59 grams)
2. Weight; heaviness; as, a person of much avoirdupois

This word dates to the 1650's as a misspelling of Middle English avoir-de-peise which dates to the 1300's. Originally it derives from Old French avoir de pois ("goods of weight") from aveir + peis ("property, goods" + "weight"). Peis comes from Latin pensum, the neuter of pendere ("to weigh") from Proto-Indo-European *(s)pen(d)- ("to pull, stretch").
By the early 16th century avoirdupois was the standard system of weights used in England for all goods except precious metals, precious stones, and medicine. Eventually it was partially replaced by the International System of Units, but some remnants are still in daily use (i.e. the stone is 14lbs). It is still the system of weights (mass) we use in the United States based on the pound made up of 16 ounces.

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Monday, May 30
Etymologies come from the Oxford English Dictionary and/or Etymonline.com 

Understand

Understand \uhn-der-STAND\ verb;

The origin of understand is Old English understandan. It meant "comprehend, grasp the idea of," but was probably literally "stand in the midst of" from under + standan ("stand"). In this context, under doesn't mean "beneath" like it usually would. This under likely comes from Old English under from Proto-Indo-European *nter- ("between, among").
However, that interpretation is up for debate. Some say that the prefix under and the preposition under are the same word with different meanings. As a prefix the word seems to have been lost in time, but similar Old English forms carried the same sense of "among" rather than "beneath." Expressions like under these circumstances carry that sense into Modern English.
Other interpretations are that the sense is really "be close to" like Greek epistamai (literally "I stand upon," actually "I know how, I know") or "stand before" like German verstehen ("understand").

Vertiginous

Vertiginous \vur-TIJ-uh-nuhs\ , adjective;
1. Affected with vertigo; giddy; dizzy
2. Causing or tending to cause dizziness
3. Turning round; whirling; revolving
4. Inclined to change quickly or frequently; inconstant

This word dates to the 1600's from French vertigineux, which derives from Latin vertiginosus ("suffering from dizziness"). Vertiginosus comes from Latin vertigo (originally "a whirling or spinning movement," later "dizziness") from vertere ("to turn") which is, of course, the forebear of vertigo.

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Saturday, May 28
Etymologies come from the Oxford English Dictionary and/or Etymonline.com 

Usufruct

Usufruct \YOO-zoo-fruhkt\ or \YOO-soo-fruhkt\ or \YOOZ-yoo-fruhkt\ or \YOOS-yoo-fruhkt\, noun;
1. Roman and Civil Law: The right of enjoying all the advantages derivable from the use of something that belongs to another, as far as is compatible with the substance of the thing not being destroyed or injured

This word dates to the 1610's from Late Latin usufructus, which is an elision of usus et fructus ("use and enjoyment"). Usus means "use" and fructus literally means "fruit," but it actually conveys a sense of "enjoyment".

Allege

Allege \uh-LEJ\ , verb;
1. To assert without proof
2. To declare with positiveness; affirm; assert
3. To declare before a court or elsewhere, as if under oath

This word dates to the 1300's and is taken from two French words. Anglo-French aleger provided the form, but Old French eslegier provided the definition: "aquit, clear of charges in a lawsuit." Eslegier derives from Latin ex- + litigare ("out of" + "bring suit"). Somewhere along the way it acquired the meaning of French alléguire, which comes from Latin allegare ("send for, the bring forth, name, produce in evidence") from ad- + legare ("to" + "to depute, send").

Wretch

Wretch \rech\ , noun;
1. A deplorably unfortunate or unhappy person
2. A person of despicable or base character

The origin of wretch is Old English wrecca ("wretch, stranger, exile") from Proto-Germanic *wrakjan. Wrecca is related to Old English wreccan ("to drive out, punish"), which is the forebear of wreak. The meaning "vile, despicable person" developed in Old English as a reflection of the sorry state of an outcast.