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-) + second element from PIE root *pag- "to fasten," source of pangere "to fasten" (see pact).
