Why Can't I Registera Blog with the Name 'Blogs'?

Hi,

I have disabled the following names in BP Magazine theme in Site Admin > Options :
www web root admin main invite administrator members register activate search activity forums groups

However, I wish to register the name 'blogs'. But when I try to register with this name the following error occurs:

1. Only lowercase letters and number allowed

2. This name is not allowed

Is the name 'blogs' banned from being used? If so, why is this and is there anyway around it?