1 : to reproduce or cause to reproduce biologically : multiply
2 : to cause to spread : extend
*3 : to foster growing knowledge of, familiarity with, or acceptance of (as an idea or belief) : publicize
The origins of "propagate" are firmly rooted in the field of horticulture. The word was borrowed into English in the late 16th century from Latin "propagatus," the past participle of the verb "propagare," which means "to set (onto a plant) a small shoot or twig cut for planting or grafting." "Propagare," in turn, derives from "propages," meaning "layer (of a plant), slip, offspring." It makes sense, therefore, that the earliest uses of "propagate" referred to facilitating reproduction of a plant or animal. Nowadays, however, the meaning of “propagate” can extend to the "reproduction" of something intangible, such as an idea or belief. Incidentally, "propaganda" also comes to us from "propagare," although it took a somewhat different route into English.