"marriage within the tribe or group," 1865, from endo- on model of polygamy. Related: Endogamous (1865). Opposed to exogamy. Apparently both were coined by Scottish anthropologist John Ferguson McLennan (1827-1881) in "Primitive Marriage."
To this law, the converse of caste, forbidding marriage within the tribe, Mr. M'Lennan has given the name of exogamy: while, instead of caste, since that word involves notions unconnected with marriage, he has used the correlative word — endogamy. [review in The Lancet, March 25, 1865]
1898, from German Heroin, coined 1898 as trademark registered by Friedrich Bayer & Co. for their morphine substitute. According to tradition the word was coined with chemical suffix -ine (2) (German -in) + Greek hērōs "hero" (see hero (n.1)) because of the euphoric feeling the drug provides, but no evidence for this seems to have been found so far.
A new hypnotic, to which the name of 'heroin' has been given, has been tried in the medical clinic of Professor Gerhardt in Berlin. [The Lancet, Dec. 3, 1898]
1610s, of persons, "controlled by conscience, governed by the known rules of right and wrong;" of conduct, etc., "regulated by conscience," 1630s, from French conscientieux (16c.; Modern French consciencieux), from Medieval Latin conscientiosus, from Latin conscientia "sense of right, moral sense" (see conscience). Related: Conscientiously; conscientiousness.
Conscientious objector is from 1896, in reference to those with religious scruples about mandatory vaccination. Military sense predominated from World War I.
After a chequered career full of startling episodes and reversals, the Vaccination Bill becomes virtually the Vaccination Act. In Parliament the hottest of the contest centred round the conscientious objector. [The Lancet, Aug. 13, 1898]
Slang shortening conchy is attested from 1917.
"inducing erotic sensation or sexual desire," 1889, from Greek eros "sexual love" (see Eros) + -genous "producing." A slightly earlier variant was erogenic (1887), from French érogénique. Both, as OED laments, are improperly formed. Erogenous zone attested by 1905.
In this connection reference may be made to the well-known fact that in some hysterical subjects there are so-called "erogenous zones" simple pressure on which suffices to evoke the complete orgasm. There is, perhaps, some significance, from our present point of view, in the fact that, as emphasized by Savill ("Hysterical Skin Symptoms," Lancet, January 30 1904) the skin is one of the very best places to study hysteria. [Havelock Ellis, "Studies in the Psychology of Sex," 1914]
by 1839 as "hospital, usually private, for the treatment of invalids, convalescents, etc., who might benefit from open air;" by 1842 as "place to which people go for the sake of health or to regain health;" 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."
Many of his patients had asked him what this hard word sanatorium meant, and he explained to them, that it was a lodging-house, which was, in fact, the proper alias of sanatorium, and that it was to the benefit of Dr. Arnott's stove and of regularity in the time of giving medicine. [from report on a "Debate on the Sanatorium" in The Lancet, Jan. 11, 1840]
also cleptomania, 1830, formed from mania + Greek kleptes "thief, a cheater," from kleptein "to steal, act secretly," from PIE *klep- "to steal" (an extension of root *kel- (1) "to cover, conceal, save"); cognate with Latin clepere "to steal, listen secretly to," Old Prussian au-klipts "hidden," Old Church Slavonic poklopu "cover, wrapping," Gothic hlifan "to steal," hliftus "thief."
The word was much-derided in 19c. as a fancy term for old-fashioned thievery and an opportunity for the privileged to claim a psychological motive for criminal misbehavior.
There is a popular belief that some of the criminal laws under which the poor are rigorously punished are susceptible of remarkable elasticity when the peccadilloes of the rich are brought under judgment, and that there is some truth in the old adage which declares that "one man may steal a horse where another dare not look over the hedge." This unwholesome distrust is not likely to diminish if, in cases of criminal prosecutions where so-called respectable persons commit theft without sufficiently obvious motive for the act, they have their crime extenuated on the plea of kleptomania, as has recently occurred in several notable instances. ["Kleptomania," The Lancet, Nov. 16, 1861]