How to Permanently solve MySQL error 2002 (HY000)
You have a memory problem, something very typical in a memory-bound system, and that can be confirmed on the line:

150207 17:31:42 InnoDB: Fatal error: cannot allocate memory for the buffer pool


As InnoDB cannot allocate memory for its buffer pool, it fails, and MySQL cannot start if the InnoDB engine fails (MySQL 5.5).

Nothing on your my.cnf seems out of the ordinary, but given that you only have 2GBs of ram, and if I understand it correctly, that is shared with the OS and a PHP/Wordpress installation, you have to be very conservative. MySQL is already taking 1.2 GB for the buffer pool, you should monitor the memory usage (top, ps) and making sure MySQL is the process to blame (compared to, for example, Apache). If it is, reduce your innodb_buffer_pool_size and/or some of the other buffers, such as the key cache or the query cache. I would set the buffer pool to ~500MB for this non-dedicated server.

You seem to be running 5.5, for other folks running 5.6, one of the main causes I have seen in MySQL support regarding out of memory killings in small-memory systems is the extra static memory needed for the performance_schema. In those cases, I recommend disabling it or reducing max_connections to avoid too much overhead.