Especially judging from Blue_eyed_son's previous question, I think that it's from PDL (see maximum_n_ind). Unfortunately, I don't know anything about PDL, so I can't understand the linked description (especially since the example usage doesn't seem actually to involve maximum_n_ind); but I think it's meant to give the indices, not just of the least element, but of the least $n elements (where $n is passed in somehow).