early 14c., conning, "learned, skillful, possessing knowledge," present participle of connen, cunnen "to know," from Old English cunnan (see can (v.1)), from PIE root *gno- "to know." Also compare cun (v.). Sense of "skillfully deceitful, characterized by crafty ingenuity" is probably by late 14c. Related: Cunningly.
c. 1300, conninge, "knowledge, understanding, information, learning," a sense now obsolete, verbal noun from connen, cunnen "to have ability or capacity," from Old English cunnan (see can v.1). By mid-14c. as "ability to understand, intelligence; wisdom, prudence;" sense of "cleverness, shrewdness, practical skill in a secret or crafty manner" is by late 14c.