estavelle
A hole that may function as an ephemeral spring or a sinkhole, depending on hydrological conditions.
The water pressure within the earth can force a swallow hole to become a spring and vice versa. These reversible sinks, which geologists call by the French geologic term estavelle, change their direction of flow (swallow or discharge) based on fluctuations in the water table.
Where it comes from
From French estavelle, which is in turn from l'Estavelle, a spring in Hérault. The place name may come from Occitan estable (“stable”) or estervel (“whirlpool”), though this is uncertain.
Adapted from the Wiktionary entry estavelle (CC BY-SA 4.0).