If you are pusillanimous, you have a small soul or weak spirit, one with few reserves of strength with which to resist the slings and arrows of outrageous fortune. The implications are of utter spinelessness and a contemptible lack of courage. Its origin lies in the old ecclesiastical Latin pusillanimis (translating a Greek term), which was formed from pusillus, very small, and animus, the soul or mind.
It first appeared in the sixteenth century and is still very much with us, though it’s a writer’s word, hardly one you’re likely to hear in your local bar unless the patrons are literary types. Back in the 1970s US Vice President Spiro Agnew famously accused his opponents of “pusillanimous pussyfooting.” In 1936, the humorist A P Herbert wrote in What a Word that “Modern dictionaries are pusillanimous works, preferring feebly to record what has been done than to say what ought to be done.” (He wrote in the same book, “American slang is one part natural growth and nine parts a nervous disorder.” But then he wasn’t much in favour of American English of any kind.)
Pusillanimous is a fine word to disparage your enemies with, one that rolls extravagantly off the tongue. Its unusualness makes it all the more effective.