μαστός

Etymology
Perhaps related to. If so, then from.

Noun

 * 1)   The human breast.
 * 2)   An udder.
 * 3) The breast.
 * 4)  Any round, breast-shaped object:
 * 5) A round hill or knoll.
 * 6) A round piece of wool fastened to the edge of nets.
 * 7)  A breast-shaped cup.

Usage notes
All usage contradicts the statement of the Grammarians that is the man's breast,  the woman's.

Etymology
From.

Noun

 * 1)  breast mammary gland
 * 2)  udder