late 14c., "intervening, interposed;" early 15c., "with nothing interposed; direct," also with reference to time, "without delay, instant," from Old French immediat (14c.), from Late Latin immediatus "without anything between," from assimilated form of in- "not, opposite of" (see in- (1)) + mediatus "in the middle" (see mediate).
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.