"of sound mind, mentally sound; free from disorder," 1721, a back-formation from sanity or else from Latin sanus "sound, healthy," in figurative or transferred use, "of sound mind, rational, sane," also, of style, "correct;" of uncertain origin. Perhaps from PIE *seh-no- from *seh- "to tie." That reconstruction "is purely mechanical," according to de Vaan, the meaning might be "which is in place, in order." Or it could be from a different root meaning "to satisfy" as in Latin satis "enough." Used earlier, of the body, with the sense of "healthy" (1620s). Related: Sanely.
1829, literally "place dedicated to health," from neuter of Modern Latin *sanitarius, from Latin sanitas "health," from sanus "healthy; sane" (see sane).
early 15c., "healthy condition," from Old French sanité "health," from Latin sanitatem (nominative sanitas) "health, sanity," from sanus "healthy; sane" (see sane). Meaning "soundness of mind" is attested from c. 1600.
"place to which people go for the sake of health or to regain health; hospital, usually private, for the treatment of patients not beyond hope of a cure," 1839, Modern Latin, noun use of neuter of Late Latin adjective sanitorius "health-giving," from Latin sanat-, past participle stem of sanare "to heal," from sanus "well, healthy, sane" (see sane). Latin sanare is the source of Italian sanare, Spanish sanar. Century Dictionary  notes it was "specifically applied to military stations on the mountains or tablelands of tropical countries, with climates suited to the health of Europeans."
c. 1600, Latin, literally "a sound mind in a sound body," a line found in Juvenal, "Satires," x.356.
Mens sana in corpore sano is a contradiction in terms, the fantasy of a Mr. Have-your-cake-and-eat-it. No sane man can afford to dispense with debilitating pleasures; no ascetic can be considered reliably sane. Hitler was the archetype of the abstemious man. When the other krauts saw him drink water in the Beer Hall they should have known he was not to be trusted. [A.J. Liebling, "Between Meals," 1962]
from the title of Joseph Heller's 1961 novel. In widespread use only after release of the movie based on the book in 1970. The catch (n.) is that a bomber pilot is insane if he flies combat missions without asking to be relieved from duty and thus is eligible to be relieved from duty. But asking to be relieved from duty indicates sanity and thus he must keep flying missions.
There was only one catch and that was Catch-22, which specified that a concern for one's safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn't, but if he was sane he had to fly them. If he flew them he was crazy and didn't have to; but if he didn't want to he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle.
"That's some catch, that Catch-22," he observed.
"It's the best there is," Doc Daneeka agreed.
The modern system of salesmanship has become so much like persecution reduced to a science, that it is quite a luxury to be allowed the use of your own discretion, without being dragooned, by a shopkeeper's deputy, into looking at what you do not care to see, or buying what you would not have. A man in his sane mind, with the usual organs of speech, has a right to be treated as if he knows what he wants, and is able to ask for it. [The Literary World, Feb. 26, 1853]
Old English wis "learned, sagacious, cunning; sane; prudent, discreet; experienced; having the power of discerning and judging rightly," from Proto-Germanic *wissaz (source also of Old Saxon, Old Frisian wis, Old Norse viss, Dutch wijs, German weise "wise"), from past-participle adjective *wittos of PIE root *weid- "to see" (hence "to know"). Modern slang meaning "aware, cunning" first attested 1896. Related to the source of Old English witan "to know, wit."
A wise man has no extensive knowledge; He who has extensive knowledge is not a wise man. [Lao-tzu, "Tao te Ching," c. 550 B.C.E.]
Wise man was in Old English. Wise guy is attested from 1896, American English; wise-ass (n.) by 1966, American English (probably a literal sense is intended by the phrase in the 1607 comedy "Westward Hoe" by Dekker and Webster). Wisenheimer, with mock German or Yiddish surname suffix, first recorded 1904.