1570s, "to marry one another," from inter- + marry (v.). Meaning "to marry across families, castes, tribes, etc." is from 1610s. Related: Intermarried; intermarrying.
Entries linking to intermarry
inter-
word-forming element used freely in English, "between, among, during," from Latin inter (prep., adv.) "among, between, betwixt, in the midst of" (also used extensively as a prefix), from PIE *enter "between, among" (source also of Sanskrit antar, Old Persian antar "among, between," Greek entera (plural) "intestines," Old Irish eter, Old Welsh ithr "among, between," Gothic undar, Old English under "under"), a comparative of root *en "in."
A living prefix in English from 15c. and used with Germanic as well as Latinate words. Spelled entre- in French; most words borrowed into English in that form were re-spelled 16c. to conform with Latin except entertain, enterprise. In Latin, spelling shifted to intel- before -l-, hence intelligence, etc.
marry v.
c. 1300, marien, of parents or superiors, "to give (offspring) in marriage," also intransitive, "to enter into the conjugal state, take a husband or wife," from Old French marier "to get married; to marry off, give in marriage; to bring together in marriage," from Latin marītāre "to wed, marry, give in marriage" (source of Italian maritare, Spanish and Portuguese maridar), from marītus (n.) "married man, husband," which is of uncertain origin.
Perhaps ultimately "provided with a *mari," a young woman, from PIE *mari-, *mori- "young wife, young woman" (source also of Welsh morwyn "girl, maiden," Middle Welsh merch "daughter"), akin to *meryo- "young man" (source of Sanskrit marya- "young man, suitor").
By early 14c. as "to take (someone) in marriage, take for a husband or wife;" by late 14c. as "become husband and wife according to law or custom; get married (to one another)." Transitive sense, of a priest, etc., who performs the rite of marriage, "to unite in wedlock or matrimony," by 1520s.
Figurative meaning "unite intimately or by some close bond of connection" is from early 15c. Related: Married; marrying. Phrase the marrying kind, describing one inclined toward marriage and almost always used with a negative, is attested by 1824, probably short for marrying kind of men, which is from a popular 1756 essay by Chesterfield.
In some Indo-European languages there were distinct "marry" verbs for men and women, though some of these have become generalized. Compare Latin ducere uxorem (of men), literally "to lead a wife;" nubere (of women), perhaps originally "to veil" [Buck]. Also compare Old Norse kvangask (of men) from kvan "wife" (see quean), so, "take a wife;" giptask (of women), from gipta, a specialized use of "to give" (see gift (n.)), so, "to be given."