Why does drush en node_clone end up in a circle this pretty much says it all:

drush en node_clone
node_clone was not found.                                                                                                                           [warning]
The following projects provide some or all of the extensions not found:                                                                             [ok]
node_clone
Would you like to download them? (y/n): y
Install location /xxx/sites/all/modules/node_clone already exists. Do you want to overwrite it? (y/n): y
Project node_clone (7.x-1.0) downloaded to /xxx/sites/all/modules/node_clone.                            [success]
Project node_clone contains a module named clone.
node_clone was not found.                                                                                                                           [warning]
The following projects provide some or all of the extensions not found:                                                                             [ok]
node_clone
Would you like to download them? (y/n): y
Install location /xxx/sites/all/modules/node_clone already exists. Do you want to overwrite it? (y/n): n
Skip installation of node_clone to /xxx/sites/all/modules/node_clone.                                    [warning]
node_clone was not found.                                                                                                                           [warning]
The following projects provide some or all of the extensions not found:                                                                             [ok]
node_clone
Would you like to download them? (y/n): n
Seems this has been well answered in drupal.org

Commands need to be

drush dl node_clone

but

drush en clone

Discussions about the 'naming standards' are here