天鼠之双刀 [tenso no soutou] or 'twin blades of the bat' in Japanese. Note that the word used for 'bat' is archaic and not commonly in use.
A Realm Reborn

Stats: PDMG 51, MDMG 38, ATK 43.5, Delay 2.6, DPS 17, DEX +42, VIT +49, Crit rate +31, Determination +31, Morale +25
Equip Level: 50, Equip On: ROG, NIN
Item Level: 110, Rarity: Green
Buy: 8,250 Wolf Mark (sell: 458 gil)
Shop: Storm Private / The Braveheart
Desynthesis results: ?
Type: Rogue's Arm, Stack: 1, Unique: Yes, Untradeable: Yes, Binding: Yes
Dye: No, FC Crest: No, Materia Slots: 2, Convert: No, Desynthesis: Yes
Glamour: Smithing, Repair: 80 gil / Grade 5, BSM40
Other: Materia effects active during PvP only. While in PvP areas, item level increases an amount equivalent to current Morale rating.
Category: Equipment