Have Legs Meaning
(nautical) To have speed.
Example: 2007, Pete Williams, How to Turn Your Million Dollar Idea Into a Reality (page 68)
Your plan will tell you if your idea has legs and is viable.
2011, Larry Garrison, â€ŽWallace Wang, Breaking Into Acting for Dummies, The Gatekeepers
The longer a film plays (which, in show business terms, means that the film has legs), the more the theater gradually earns from ticket sales.