The Veruul is a name given to a creature in ancient Vulcan mythology that, ancient legend stated, stalked prey withn the Womb of Fire in Vulcan's Forge on Vulcan. It was said that none survived an encounter with the beast.
The Veruul is also the name of an amphibian animal that lives on the Romulan homeworld of Romulus. The creature is approximately 6.7 meters in length and lived in a watery environment, typically within ponds or shores. It possessed a scaled skin and webbed claws. It usually hid itself within the water and vegetation to prevent detection by prey, then would suddenly burst from its watery habitat and pull its prey under the water, after which it would consume it.
The creatures reproduced by laying eggs.
The early Vulcan people that would become the Romulans encountered these creatures during the initial survey of the world with a loss of an expedition member. One of the survivors of the survey party decided to name the creature a veruul after the ancient myth. (TOS - Vulcan's Soul novel: Exiles)
Approximately twenty centuries after this expedition, the name of this animal had also become a Romulan expletive in their language. William T. Riker of Starfleet compared former Romulan national Alidar Jarok to one for using such profanity in public after Jarok insulted Lieutenant Worf with Klingonese vulgarities for his mere presence, while getting medical care in Enterprise-D's sickbay. (TNG episode: "The Defector")