Steal goods from (a place or person), typically using force and in a time of war or civil disorder. The word comes (in the mid 17th century) from German plündern, literally ‘rob of household goods’, from Middle High German plunder ‘household effects’.
Early use of the verb was with reference to the Thirty Years War (reflecting German usage); on the outbreak of the Civil War in 1642, the word and activity were associated with the forces under Prince Rupert.
The well-known comment ‘What a place to plunder!’ is a misquotation (was für plündern) of the comment of the Prussian Field-Marshal Blücher (1742–1819) on London, ‘Was für Plünder! [What rubbish!]’