KELOUSE (or Celusa) was the Naiad Nymph of the springs at the source of the River Asopos in Sikyonia (southern Greece). By Poseidon she became the mother of that river. Kelouse was probably one of the Okeanides, the Nymph sources of fresh water.
Her son, Asopos, was often described as a lame, a hobbling God, whose stream ran dry in summer, which explains her two names, kêloô meaning to have an abnormal delivery, and pêroô to make lame.
PERO (Pêrô). The mother of the river god Asopus by Poseidon. (Apollod. iii. 12. § 6.)
Source: Dictionary of Greek and Roman Biography and Mythology.
Pseudo-Apollodorus, Bibliotheca 3. 156 (trans. Aldrich) (Greek mythographer C2nd A.D.) :
"The Asopos river was born of Okeanos and Tethys, or, according to Akousilaos [poet C6th B.C.], of Pero and Poseidon, while others say of Zeus and Eurynome."
Pausanias, Description of Greece 2. 12. 4 (trans. Jones) (Greek travelogue C2nd A.D.) :
"Asopos, said to be the son of Kelousa (Celusa) and Poseidon, discovered for him [Aras first king of Sikyonia] the water of the river which the present inhabitants call after him Asopos."
- Apollodorus, The Library - Greek Mythography C2nd BC
- Pausanias, Guide to Greece - Greek Geography C2nd AD