When it comes to welkin, the sky's the limit. This heavenly word has been used in English to refer to the vault of the sky for centuries, and it derives from an Old English word meaning "cloud." In current English, welkin is still flying high, and it is often teamed with the verb ring to suggest a loud noise or an exuberant expression of emotion, as in "the welkin rang with the sound of the orchestra" or "her hearty laugh made the welkin ring." These contemporary phrases echo an older use—the original words of a carol that once began "Hark, how all the welkin ring," which we now know as "Hark! The herald angels sing."