"dining hall," especially in a monastery, early 15c., refectori, from Medieval Latin refectorium, "place of refreshment," from past participle stem of reficere "to remake, restore," from re- (see re-) + combining form of facere "to make, do" (from PIE root *dhe- "to set, put").
Middle English (and after) also had it as a verb, refeten, "to refresh, restore, feed" (late 14c.), from Anglo-French refeter, Old French refactier. Also refection "refreshment, nourishment," all ultimately from Latin. Some survive in specialized senses.
For after a draught of wine, a Man may seem lighter in himself from sudden refection, although he be heavier in the balance, from a corporal and ponderous addition; but a Man in the morning is lighter in the scale, because in sleep some pounds have perspired; and is also lighter unto himself, because he is refected. [Browne, "Vulgar Errors," iv. 7]