I looked this up the other day just for the fun of it ... and because I had never paused to think why PIs used to be called gumshoes. But according to etymology.com:
"plainclothes detective," 1906, from the rubber-soled shoes they wore (which were so called from 1863); from gum (n.1) + shoe (n.).
Obvious, yes. But still fun. =) And a nice start to the week I plan on preparing my "History of Spies in Early America" home school group class. ;-) Got the Creative Writing one mostly done yesterday. Yay!
Hope everyone has a great week!