I've never seen this one before: sempiternal.
It means "seemingly everlasting," and if Wiktionary's etymology is to be believed, it's …
… from Latin sempiternus, a contraction of semperæternus, from semper (“always”) + æternus (“eternal”).
Always eternal? As opposed to, say, eternal for a fleeting moment? No wonder the Roman Empire collapsed.
Anyway, you'll be unsurprised to hear I saw it referring to Sen. Robert Byrd.