"one who fails to perform some duty or obligation," 1650s, agent noun from default (v.).
Entries linking to defaulter
default v.
late 14c., defalten, defauten, "be lacking, be missing," also "become weak," from default (n.). Restricted meaning "to fail in fulfilling or satisfying an obligation," especially a legal or pecuniary one, is from late 15c. Related: Defaulted; defaulting.