tank: [17] Tank ‘water-storage container’ originated in India, where it denoted a ‘pond’. It was borrowed from a local word, such as Gujarati tānkh or Marathi tānken ‘pond, cistern’. These in turn probably went back to Sanskrit tadāga ‘pond, lake’, which was of Dravidian origin. The word was applied as a secret code name to the new armoured vehicle at the end of 1915, supposedly because it was thought to resemble a benzene tank.
