After reading Mr. Peter Goldsbury article for shihan, which has tremendous depth, I am moved to believe the word 'Shihan' is no more than a slang word, a derivitive whose actual word is not the the meaning.
Changed meanings for each slang word, such as 'Bad' a formidable opponent, or 'fat' sometimes called 'phat' someone who has much of what others appreciate such as money, looks, good luck, etc ... would seem to be the vein of the word 'shihan' verses its character or rootword meaning.
Or is it merely the creation of something new from something very old?
In either case, read this fascinating article with its invaluable insight into this question.
I think we should all chip in and by the guy a day out for his efforts, but that is the way I feel about knowledge.