From the Greek litos meaning ‘small’, the rhetorical use of understatement (diminishing) to imply the opposite. For example, “He was not a little concerned at the loss of his fortune.”
Editors. "Litotes". The Literary Encyclopedia. First published 01 November 2001; last revised 30 November -1.
[http://www.litencyc.com/php/stopics.php?rec=true&UID=668, accessed 27 April 2015.]