apert adj.

early 14c., "open; unfastened" (originally literal, of clothing, a book, etc.; this sense is now obsolete), from Old French overt (Modern French ouvert), past participle of ovrir "to open," from Latin aperire "to open, uncover," from PIE compound *ap-wer-yo- from *ap- "off, away" (see apo-) + root *wer- (4) "to cover." Compare Latin operire "to cover," from the same root with PIE prefix *op- "over;" and Lithuanian atverti "open," užverti "shut." The meaning "clear, open or plain to view, manifest, revealed" is from late 14c.