Lewis & Short

favīsae or favissae, ārum, f., underground reservoirs or cellars near the temples, for water or for sacred utensils no longer in use, Varr. ap. Gell. 2, 10; Paul. ex Fest. s. h. v., p. 88, 4 Müll.; cf.: favissae, θησαυροί, Gloss. Philox.