pug 2 
(pŭg)
(pŭg)n.
1. Clay ground and kneaded with water into a plastic consistency for forming bricks or pottery.
2. A machine for grinding and mixing clay.
tr.v. pugged, pug·ging, pugs
1. To work or knead (clay) with water.
2. To fill in with clay or mortar.
3. To make soundproof by covering or packing with clay, mortar, sawdust, or felt.
[Origin unknown.]