"lose the ability to maintain compensation," 1912, probably a back-formation from decompensation. Related: Decompensated; decompensating.
"personal qualities, gifts of ability, share of mental endowments or acquirements," 1560s, from part (n.).
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.