[European crow], Middle English roke, from Old English hroc, from Proto-Germanic *khrokaz (source also of Old Norse hrokr, Middle Dutch roec, Dutch roek, Middle Swedish roka, Old High German hruoh "crow"), probably imitative of its raucous voice. Compare crow (n.), also Gaelic roc "croak," Sanskrit kruc "to cry out." Used as a disparaging term for persons at least since c. 1500, and extended by 1570s to mean "a cheat," especially at cards or dice, also, later "a simpleton, a gull, one liable to be cheated" (1590s). For sense, compare gull (n.2).
word-forming element making nouns meaning "place for, art of, condition of, quantity of," from Middle English -erie, from Latin -arius (see -ary). Also sometimes in modern colloquial use "the collectivity of" or "an example of."
<a href="https://www.etymonline.com/word/rookery">Etymology of rookery by etymonline</a>
Harper, D. (n.d.). Etymology of rookery. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rookery