David Kazdan wrote:
The singularities in the function are called the "poles," after an
analogue computing technique used in the 1930s for finding those
points.

I thought they were called poles because if you made a surface plot of
z(x,y), it looked like a big tent, and the sigularities were like the
spikes where the tent poles stuck through.

I'm sure I'm dating myself, but I actually used analog computers in
college. The EE lab had a bunch of them for control systems work. It
was kind of fun programing systems of differential equations by plugging
patch cords into a big plugboard and watching the answer get drawn on a
scope. I wouldn't be surprised if the aerodynamics of most of the light
planes we fly today were worked out on exactly such machines.

Hmmmm. Just did some googling. The more I look at the picture, the
more I'm convinced it was a TR-20 we must have been using. We also had
a TR-48 in the lab, but most students didn't get to use that.

http://dcoward.best.vwh.net/analog/eai.htm