From Middle English cove, from Old English cofa ("chamber; den"), from Proto-Germanic *kubĂ´. Cognate with German Koben, Swedish kova. This word has probably survived as long as it has due to its coincidental phonetic resemblence to the unrelated word "cave".
Britain ante-1570. From Romani kodo ("this one, him"), perhaps change in consonants due to lower class th-fronting, or Romani kova ("that person").