Emily Dickinson Lexicon

COM-MAND'ER, n.

1. A chief; one who has supreme authority; a leader; the chief officer of an army, or of any division of it. The term may also be applied to the admiral of a fleet, or of a squadron, or to any supreme officer; as, the commander of the land or of the naval force; the commander of a ship.
2. One on whom is bestowed a benefice or commandry.
3. A heavy beetle or wooden mallet, used in paving, &c. [This gives us the primary sense of L. mando, to send, to drive.]
4. An instrument of surgery. – Wiseman.