SC - igrounden

[Seton1355 at aol.com]

I am reading through CURYE ON INGLYSCH and have run into this word:   
*igrounden* does it mean *ground*  as in ground up? that seems to make sense 
to the context and there was another word  (can't find it now) that was a 
"regular english word" except for starting with *i*.  Does *i* signify 
something special?

Also, I've run into the *th* symbol for thorn  (thanks list. I would never 
have known what it was if it weren't for you guys!)  But what is that symbol 
that looks kinda like a squiggly 3?
Thanks
Phillipa Seton