BMiner seems to be misreporting the worker name, if that's where it comes from. This is particular to MPH so far. It seems that when I switch to Excavator, the worker name appears correctly in the Pools tab.
The Bminer API interface only reports pool URL but no worker information. Awesome Miner is then trying to be smart and guess the correct worker name based on the command line you passed. However, for this miner Awesome Miner wasn't doing it correctly, resulting in an incorrect display of worker name. This is a display issue only and doesn't affect the mining - as you probably already verified via the command line used to start Bminer.
I will correct this in the next release. Thanks for reporting it.