1560s, "to cause to multiply by natural generation or reproduction" (transitive), from Latin propagatus, past participle 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, from PIE root *pag- "to fasten," source of pangere "to fasten" (see pact). Intransitive sense "reproduce one's kind" is from c. 1600. The meaning "spread from place to place or person to person" (of a belief, doctrine, etc.) is from c. 1600. Related: Propagated; propagating.