The expression by Jingo is a minced oath that appeared rarely in print, but which may be traced as far back as to at least the 17th century in a transparent euphemism for "by Jesus".
[1] The OED attests the first appearance in 1694, in an English edition of the works of François Rabelais as a translation for the French par Dieu!
[citation needed] The chorus of an 1878 song [3] by G. H. MacDermott (singer) and George William Hunt (songwriter) commonly sung in pubs and music halls of the Victorian era gave birth to the term "jingoism".
[4] The song's lyrics had the chorus: 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.
The phrase also appears in Chapter 16 of Robert Louis Stevenson's The Wrong Box when John recognizes his Uncle Joseph whom he had believed to be dead.
When Benito Mussolini was threatening to invade Abyssinia in 1935, the British comic magazine Punch published a parody: We don't want you to fight but by Jingo if you do, We will probably issue a joint memorandum suggesting a mild disapproval of you.