The Spanish word casilla may mean 'an outhouse' or 'an outdoor toilet'. In Chabacano, this word becomes casillas (with an 's'), and it means 'toilet'. To some, a distinction exists between casillas and baño (baño being indoors and casillas outdoors) but there are people who apply the word casillas to toilets in general (whether they are indoors or outdoors).
These words (baño and casillas) are mostly used to refer to toilets at home. When in public, people prefer to use the words 'toilet' or 'CR'. I’m not sure about other Zamboangueños, but I feel like it’s a bit too vulgar if I ask where the baño or the casillas is when I’m in a mall. 😂
Here are some words using the Chabacano casillas.
Chabacano: Donde el casillas?
English: Where is the toilet?
Chabacano: Puede tu limpia (con) el casillas?
English: Can you clean the toilet?
Chabacano: Aquel ba el casillas?
English: Is that the toilet?
In Camins’ dictionary, he defines the word casillas as a stool outhouse. This word is pronounced as kasilyas.