1718, "committee of cardinals in charge of Catholic missionary work," short for Congregatio de Propaganda Fide "congregation for propagating the faith," a committee of cardinals established 1622 by Gregory XV to supervise foreign missions. The word is properly the ablative fem. gerundive of Latin propagare (see propagation). Hence, "any movement to propagate some practice or ideology" (1790). Modern political sense dates from World War I, not originally pejorative. Meaning "material or information propagated to advance a cause, etc." is from 1929.
1560s, "to cause to multiply," from Latin propagatus, past participle of propagare "to set forward, extend, procreate" (see propagation). Intransitive sense "reproduce one's kind" is from c.1600. Related: Propagated; propagating.
mid-15c., from Old French propagacion "offshoot, offspring" (13c.) and directly from Latin propagationem (nominative propagatio) "a propagation, extension, enlargement," noun of action from past participle stem of propagare "set forward, extend, spread, increase; multiply plants by layers, breed," from propago (genitive propaginis) "that which propagates, offspring," from pro- "forth" (see pro-) + *pag-, root of pangere "to fasten" (see pact).