I looked up Sear in a book I have titled; Webster's New World Dictionary of the American Language, 1965 Edition.

4 definitions were listed, none appling to a gun part;
1; To dry up, wither
2; To scorch or burn the surface of
3; To brand with a hot iron
4; To make Callous or UnFeeling

I have no idea just who but I think someone applied definition 4 to Wonko.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra