Sniddle is a word that was used in past centuries in the UK to refer to sedges and other coarse grasses, particularly those growing in wet areas. It comes from the Middle English snithil or snyth hill, and its meaning has not changed in the last 600 years.
These days sniddle is most often used in place names such as Sniddle Farm and Sniddle Hey, and plant names, such as Sniddle Moss and Sniddle Flock (more commonly known as Cotton Grass).
Sniddle has the dubious distinction of not appearing anywhere in any of the writings of E2, other than this one; you might be surprised to find how few words this is true of.