Webster's Revised Unabridged Dictionary · 1913

Muller

Muller , noun

1.
One who, or that which, mulls.
2.
A vessel in which wine, etc., is mulled over a fire.

Muller , noun

[Old English mullen to pulverize, bruise; compare Icelandic mylja; prob. akin to English mold soil. See Mold soil, and compare Mull dirt.]

A stone or thick lump of glass, or kind of pestle, flat at the bottom, used for grinding pigments or drugs, etc., upon a slab of similar material.