poles 
[Mar. 21st, 201211:56 am]
Tobin Fricke's Lab Notebook

Bernard Friedland's explanation of the origin of the word "pole" (in Control System Design):The roots of the denominator [of a rational function] are called the poles of the transfer function because H(s) becomes infinite at these complex frequencies and a contour map of the complex plane appears as if it has poles sticking up from these points. [emphasis mine] 

