My elderly dictionary+ has the word "jingo" defined as "a term used in a vulgar oath" and "jingoism" as "the military spirit of England as represented by so-called Jingoes".
These days, "Jingoism" is defined as "patriotism in the form of aggressive foreign policy".
The word apparently has it's origin in a song that was popular in Victorian Music Halls in Britain during the Russo-Turkish War of 1877 to 1878. It was performed by the singer Gilbert Hastings MacDermott (1845 - 1901). The song was written by the songwriter George William Hunt (1839 - 1904) and in the chorus the words "by Jingo" were used in order to avoid blaspheming:
"We don't want to fight but by Jingo if we do
We've got the ships, we've got the men, we've got the money too
We've fought the Bear* before, and while we're Britons true
The Russians shall not have Constantinople."
We've fought the Bear* before, and while we're Britons true
The Russians shall not have Constantinople."
*The Russians - in the Crimean War…
The song was brought back several times and with altered words was also popular during the First World War.
Sources: http://www.victorianweb.org/mt/musichall/macdermott1.html
http://www.cyberussr.com/hcunn/q-jingo.html - full text of the song
G.W. Hunt's songs - http://www.themusichallguild.com/artist.php?id=258
+ Nutall's Standard English Dictionary of the English Language, William Clowes and Son, London
+ Nutall's Standard English Dictionary of the English Language, William Clowes and Son, London
