While The CW still hasn't revealed the official title for the forthcoming The Flash/Arrow spiinoff featuring Brandon Routh, Caity Lotz and Victor Garber, it seems as though The Flash recurring guest star John Wesley Shipp may have let the name slip at a convention appearance this weekend.
Early reports were that the show would bypass a pilot production and go straight to series, so Shipp's claims gel with those rumors.
Legends was a late-1980s crossover event from DC Comics that pitted Darkseid against The Phantom Stranger in a wager that the lord of Apokolips could turn earth against its heroes. To that end, he embedded one of his minions in the press and launched an aggressive propaganda campaign against superheroes.
Years later, Legends of the DC Universe was an anthology-style monthly comic series that saw numerous heroes filter in and out, with creators telling stories that didn't have to function within the then-current status quo of the DCU. The series ran for 41 issues plus an oversized Crisis on Infinite Earths tie-in one-shot.
Legends is the title of a show currently airing on TNT, which would make this name an odd choice. GATV suggest that it's possible this is either a working title or just a single word of a longer title.
It's likely fans can expect a formal title announcement and perhaps some additional details about the series either during the series finale of The Flash, or at The CW's upfront presentation on May 14.