cave [ME] Latin cavus, ‘hollow’, is the origin of a number of English words, including cave, cavern [LME], cavity [M16th], and excavate [L16th]. Concave [LME] is from cavus preceded by con ‘with’, while convex [L16th] is from the Latin for ‘vaulted, arched’. In the days when more people knew Latin, there was a second English word spelled cave. This one, pronounced kah-vay, meant ‘beware!’, and was used from the mid 19th century by schoolchildren to warn their friends that a teacher was coming.