What does Boxing Day have to do with boxing?
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).
propagation prop·a·ga·tion (prŏp'ə-gā'shən)
Multiplication or increase, as by natural reproduction.
The act or process of propagating, especially the process by which an impulse is transmitted along a nerve fiber.
in horticulture, the reproduction of plants by any number of natural or artificial means