χελώνη

1. a tortoise , (Homeric Hymns); prov. of insensibility, ἰὼ χελῶναι μακάριαι τοῦ δέρματος oh ye tortoises , happy in your thick skins! (Aristophanes Comicus)

2. like Roman testudo, a pent-house formed of shields overlapping each other like the scales on a tortoise's back , used by storming parties in approaching a city's walls: then, generally, a pent-house for protecting besiegers, (Xenophon Historicus) (ML)