The Collaborative International Dictionary
Expugn
Expugn \Ex*pugn"\ ([e^]ks*p[=u]n"), v. t. [L. expugnare; ex out + pugnare to fight, pugna fight. Cf. Impugn.] To take by assault; to storm; to overcome; to vanquish; as, to expugn cities; to expugn a person by arguments.
Douglas Harper's Etymology Dictionary
expugn
early 15c., "eradicate, exterminate," also "conquer, capture by fighting," from Old French expugner, from Latin expugnare "to take by assault, storm, capture" (source also of Spanish expugnar, Italian espugnare), from ex- (see ex-) + pugnare "to fight" (see pugnacious). Related: Expugned; expugnable.
Wiktionary
expugn
vb. (context obsolete English) To take by storm; capture. (15th-17th c.)