The Beo Sword (ベオの剣 Beo no ken) is a special Sword that is unique to Fire Emblem: Thracia 776. This sword can strangely only be used by Delmud and Felgus, Felgus, who is widely rumored to be the bastard son of the mercenary Beowolf, while Delmud's reason is unknown, causing a popular fan-theory that the two are half-siblings to be born. When equipped, it grants the Wrath and Ambush skills to its wielder, which are skills that Beowolf cannot use.
* - Usable by Delmud and Felgus only.
The "Beo" portion of the sword's name could possibly be derived from Beowolf's name, further hinted at by his alleged children, Delmud and Felgus, being able to wield it. An alternate translation of the name could be "Beo's Sword", further implying, at the least, that is was owned by someone with the name or a name similar to "Beo".
Alternatively, the name of the sword could take its origins from the Irish verb "beo", that which directly translates to "live".