late 14c., resouning, "exercise of the power of reason; act or process of thinking logically;" also an instance of this, a presentation of reasons or arguments; verbal noun from reason (v.).

Middle English stonden, standen, from Old English standan "occupy a place; stand firm; congeal; stay, continue, abide; be valid, take place; oppose, resist attack; stand up, be on one's feet; consist, amount to" (class VI strong verb; past tense stod, past participle standen).

This is from Proto-Germanic *standanan, source also of Old Norse standa, Old Saxon standan, Old Frisian stonda, Gothic standan, Old High German stantan, which are related to simpler forms, such as Swedish stå, Dutch staan, also German stehen, with vowel perhaps altered by influence of gehen "go"), ultimately from PIE root *sta- "to stand, make or be firm."

The sense of "exist, be present" is attested from c. 1300. The meaning "to cost" is from mid-14c. (for sense, compare cost (v.), from Latin constare, literally "to stand at"). The meaning "be so high when standing" is from 1831.

The meaning "encounter without flinching or retreating" is from 1590s; that of "endure successfully, undergo, come through" is from c. 1600. The weaker sense of "put up with" is attested by 1620s (to not stand it is by 1750).

The meaning "submit" (to chances, etc.) is from c. 1700. The meaning "pay for as a treat" is from 1821. The sense of "become a candidate for office" is from 1550s. Nautical sense of "hold a course at sea" is from 1620s.

Stand back "keep (one's) distance" is from late 14c. To stand down is from 1680s, originally of witnesses in court; in the military sense of "come off duty" it is by 1916. To stand one's ground is by 1620s; to stand one's chances is by 1725.

Phrase stand pat (1869) is from poker, "declare one's intention to play one's hand as dealt," also figurative, earlier simply stand (1824 in other card games).

The phrase stand to reason (1620) "be reasonable; be natural, evident, or certain," is from earlier stands with reason; the notion in the verb is "adheres to, conforms with."

To let (something) stand is from c. 1200. The construction stand and (deliver, etc.) was in late Old English in Biblical translations.

1869, from French raison d'état "reason of state," thus "convenience of the government." See reason (n.) + state (n.2).

late 14c., racional, "pertaining to or springing from reason;" mid-15c., of persons, "endowed with reason, having the power of reasoning," from Old French racionel and directly from Latin rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason" (see ratio).

In arithmetic, "expressible in finite terms," 1560s. Meaning "conformable to the precepts of practical reason" is from 1630s. Related: Rationally. It is from the same source as ratio and ration; the sense in rational is aligned with that in related reason (n.), which got deformed in French.

"agreement in terminal sounds of words or metrical lines," a 16c. attempt to restore a classical spelling to Middle English ryme, rime (c. 1200) "measure, meter, rhythm," later "rhymed verse" (mid-13c.), from Old French rime (fem.), which is related to Old Provençal rim (masc.), earlier *ritme, from Latin rithmus, from Greek rhythmos "measured flow or movement, rhythm; proportion, symmetry; arrangement, order; form, shape, wise, manner; soul, disposition." This is related to rhein "to flow" (which is reconstructed in Watkins to be from PIE root *sreu- "to flow").

Compare rhythm, also see rhyme (v.). The intermediate form rhime was frequent until late 18c.

In Medieval Latin, rithmus was used for accentual, as opposed to quantitative, verse, and accentual verse usually was rhymed, hence the sense shift. In precise prosody it means the quality of agreement in end-sounds such that the last stressed vowel, and any sounds after it, are the same, and preceding sounds differ. 

Verse was invented as an aid to memory. Later it was preserved to increase pleasure by the spectacle of difficulty overcome. That it should still survive in dramatic art is a vestige of barbarism. [Stendhal "de l'Amour," 1822]

The sense of "a piece of poetry in which consonance of end-sounds is observed" is from 1610s. It is attested from 1650s as "word that rhymes with another."

The phrase rhyme or reason "good sense" (chiefly used in the negative) is from late 15c. (see reason (n.)). Rhyme scheme "ordered pattern of end-rhymes in metrical composition" is attested from 1931.

early 14c., unresoun, "lack of reason, irrationality; an injury, that which is unjustifiable;" from un- (1) "not" + reason (n.). By 1827 (Carlyle) as "absence of reason." The Abbot of Unreason of the Scottish revels is attested from late 15c.

*rē-, Proto-Indo-European root meaning "to reason, count;" a variant of PIE root *ar-, also arə-, "to fit together." 

It might form all or part of: Alfred; arraign; arithmetic; Conrad; dread; Eldred; Ethelred; hatred; hundred; kindred; logarithm; Ralph; rate (n.) "estimated value or worth;" rathskeller; ratify; ratio; ration; read; reason; rede; rhyme; riddle (n.1) "word-game;" rite; ritual.

It might also be the source of: Sanskrit radh- "to succeed, accomplish;" Greek arithmos "number, amount;" Latin reri "to consider, confirm, ratify," ritus "rite, religious custom;" Old Church Slavonic raditi "to take thought, attend to;" Old Irish im-radim "to deliberate, consider;" Old English rædan "to advise, counsel, persuade; read;" Old English, Old High German rim "number;" Old Irish rim "number," dorimu "I count."