Emily Dickinson Lexicon

TES-TU'DO, n. [L.]

1. A tortoise. Among the Romans, a cover or skreen which a body of troops formed with their shields or targets, by holding them over their heads when standing close to each other. This cover resembled the back of a tortoise, and served to shelter the men from darts, stones and other missiles. A similar defense was sometimes formed of boards and moved on wheels.
2. In medicine, a broad soft tumor between the skull and the skin, called also talpa or mole, as resembling the subterraneous windings of the tortoise or mole. Cyc.