The Omega/rainbow symbol mystery

Here's a symbol used in the land owners' books in Bohemia.  This one's from 1694, and we found it in the 1700s too...not so much after 1800.  Out of curiosity, I wrote to SRA Trebon and asked if they knew what it meant.  No one did.
Sometimes, there was only one arch, sometimes two, sometimes three.  This one was the fanciest one I found.  
We see it as the last letter of the Greek alphabet (liturgically, "the alpha and the omega", the beginning and ending), so maybe it signaled the end of something.  But then, why the difference in the number of arches? 

It seems like they used the 'rainbow' symbol early on, or perhaps it was that particular scribe's peccadillo.  The pages below are from 1760 and they're all single omega signs.  No, it doesn't stand for someone's death, as that's what the little cross meant (second circle, right).  Might it have mean a debt, paid back, or a change of houses, or equipment loaned or sold to the serf?  
It had to be something fairly common, but significant enough that it made a difference to the landowner. 
Can YOU think of anything?  Brainstorming works, ya know--leave a comment ☺.
Thanks!