Curious Math Word Of The Day: Germ

From Using Algebraic Geometry, by D. A. Cox, J. Little, and D. O’Shea:

Two analytic functions, each defined on some neighborhood of the origin, are equivalent if there is some (smaller) neighborhood of the origin on which they are equal. An equivalence class of analytic functions with respect to this relation is called a germ of an analytic function (at the origin).

This is a pretty good word to use for this purpose, given the meaning, but a peculiar choice of language nonetheless.

(Walt from Ars Mathematica points out that the word comes from wheat, which makes sense given its meaning. Other examples of agriculture-based math terminology that I can think of are the “kernel” of a map, or the “fibre” of a map.)