The Watering Hole was a saloon in Paradise City, the capital of the planet Nimbus III in 2287. Aside from alcohol, the saloon's featured a feline exotic dancer, a pool table and communications screen was located in the main room of this saloon.
A back room of this saloon was where representatives of the Federation, Klingon Empire, and Romulan Star Empire had an "office". (Star Trek V: The Final Frontier)
The name of this saloon was from a sign seen above the entrance, and its description was from the script.
According to the text commentary in the film's Special Edition DVD, "The green neon sign was designed by art director Nilo Rodis-Jamero," and continued to note that "Below the big neon sign are three smaller signs welcoming visitors in Klingon, English, and Romulan."