I just wondered if it had occurred to any Egyptologists that the Ankh used in this ceremony appeared to be exactly the same shape as the Plough/Big Dipper/Great Bear. It also is the same shape as the ankle of their sky-god Nut. I don't suppose that could be the origin of the word? If you follow the 'tail' of the plough around you get to Spisa. I don't suppose that this is the word for knee in any of those ancient languages? Rambling even further, could it be that by forming the complete circle, mouth of pharoah, ankle of sky-god, mouth of sky-god, ankle of pharoah, they felt that they could get the spirit of the pharoah up into the sky where they thought it belonged?
If you follow the tail of the Big Dipper you get to Arcturus (Alpha Bootes). I've never heard of Spisa. I have heard of Spica (Alpha Virgo iirc), but that is in a different part of the sky.
1. Ooops, mis-spelt. 2. I've been labouring under a mis-apprehension for 30 or so years which is when I knew a lot more about the stars. Ignore that paragraph. Regards to all.