Astroturfing is a word used to describe a fake or counterfeit grassroots campaign. The clever term is derived from the notion that one kind of fake grass is astroturf.
Another more niche example is from mathematics. We call the "germ" of a function the part at the bottom of a stalk in some sheaf. We call this a germ because it is like the germ for the stalk of a plant.
In both of these examples, one makes an analogy to create a term, and then related terms, carry on this analogy to build terms related to the first.
Is there a specific name for this sort of term?