"act or fact of sending messages," by 1865, verbal noun from message (v.). Middle English had messagery "the carrying of messages" (late 14c.), from Old French messagerie.
Entries linking to messaging
message v.
"to send messages," 1580s, from message (n.). Marked as "obsolete" in Century Dictionary (1895). Meaning "to send an electronic message" is by 1992. Related: Messaged; messaging.