Sentence:  One of John Maynard Keynes's most famous terms, "<WSD>animal spirits</WSD>," is another name for much the same concept as irrational exuberance‎ 
Meaning of the word marked with <WSD> tags:  After Keynes (citation 1936, above), the emotional and intuitive factors that drive business decisions whether to make investment gambles. (from 20th c.)