As did the word "gravitas" during the last presidential election, the word "jingoism" is currently coming into its own. I suspect that most of us are a little fuzzy on the definition of the term and more fuzzy on its derivation so without getting into politics, here's the skinny, which I found in both Brewer's Phrase and Fable and the Oxford English Dictionary on line (to which I have access through my public library website--you probably can use it that way, too).
First, the word jingo came from the Basque word Jainko, meaning God, so the expression "by Jingo!" is the same as "by God!" Brewer's states that this term started to be used when Basque soldiers were imported by Edward I (1239-1307) to fight in Wales.
Between that time and the Russo-Turkish War (1877-78), the adjective "jingo" was used to describe a rather vulgar person (someone who would say "by Jingo").
Jingoism means extreme nationalism characterized by shows of excessive patriotism, usually associated with going to war. This word came about when England was considering involvement in the Russo-TurkishWar. A music hall song of that time proclaimed:
Jingoism became the term for the sentiment expressed in the song and a jingoist is a person who embodies that sentiment.
By the way, that is Kate Smith singing Irving Berlin's "God Bless America," the story of which can be read here. The composer of the song, Irving Berlin, was not a jingoist but a true patriot. And, incidentally, a Jewish Russian immigrant.