interdependent adj.

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.

also dependant, late 14c., "relying for existence on;" early 15c. as "contingent, related to some condition;" from Old French dependant, present-participle adjective from dependre "to hang down," from Latin dependere "to hang from, hang down; be dependent on, be derived," from de "from, down" (see de-) + pendere "to hang, cause to hang; weigh" (from PIE root *(s)pen- "to draw, stretch, spin").

For spelling, see dependant (n.). In some cases the English word is directly from Latin dependentem (nominative dependens), present participle of dependere. From early 15c. in the literal sense of "hanging down, pendent." From 1640s as "subordinate, under the control of or needing aid from an extraneous source." Dependent variable in mathematics is recorded from 1852.

1830, from interdependent + abstract noun suffix -cy.