ref: http://www.ccel.org/j/josephus/works/war-5.htm
As a result of curiosity, I find I must correct myself: Above linked you will find Josephus, Wars of the Jews, Book Five, wherein Josephus does indeed mention 'cloisters' numerous times... as an expression of architecture - a covered colonnade or walkway - In every case... Which is why I couldn't recall it according to a convent or nunnery.
All the same, for what it's worth, I stand corrected.
Thank you, so noted; I would add that Josephus, Chapter 4, paragraph 3, clearly shows rooms and bathing rooms built over one of the cloisters. I would further add the term "cloistered life" is related to the architecture with respect to religious buildings.