Summary: A salty phrase with roots in Ancient Rome has confounded English speakers for centuries. Join<strong> Slate Plus</strong>! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today at <a href="http://www.slate.com/podcastsplus">www.slate.com/podcastsplus</a>. Twitter: @lexiconvalleyFacebook: facebook.com/LexiconValleyEmail: <a href="mailto:lexiconvalley@slate.com">lexiconvalley@slate.com</a>
