c. 1600, from immediate + abstract noun suffix -cy. Middle English had immediacioun "close connection, proximity" (mid-15c.).
Entries linking to immediacy
immediate adj.
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).
-cy
abstract noun suffix of quality or rank, from Latin -cia, -tia, from Greek -kia, -tia, from abstract ending -ia (see -ia) + stem ending -c- or -t-. The native correspondents are -ship, -hood.