MEANING:
noun: A timid, unassertive person.
ETYMOLOGY:
After Caspar Milquetoast, a comic strip character by H.T. Webster (1885-1952). A synonym of the word is milksop. Earliest documented use: 1932.
USAGE:
"Martin Oberman: This is a very tough place. You can't be a milquetoast."
Peter Slevin; Testing Rahm; The Washington Post; Sep 13, 2012.