Complex question... it seems LH used to have a magic secret top level early in their history called 'Hon.', derived from 'honoris causa', ie a title that was awarded, not earned, similar to an honorary degree. In 2004 when they reorganised M&M, they had various plans to reward the überflyers out of which the HON level was born. This was told to me by some people at M&M whom I specifically asked about the weird term and most importantly to check if they really had considered 'IMP' (see this thread for details: http://www.flyertalk.com/forum/archive/t-69352.html)

The 'circle' came from AFAIK the former swiss travel club, which had a top level with that phrase. LH was at the time busy integrating LX/SR into the happy LH family and was looking for ways to appease the horrified Swiss elite that saw their self financed SR experiment fail and LH take over.