Boyd’s Bible Dictionary:
(hulls). The original means the carob, or locust bean (Luke 15:16).
Concise Bible Dictionary:
In the Old Testament it is the skin of grapes (Num. 6:4; see 2 Kings 4:42, margin). In the New Testament it is κερἀτιον, which is the fruit, not the husk, of the carob tree. It is abundant in Syria, and the pods, containing a sweet pith-like substance, are food for cattle and pigs: it is occasionally eaten by the very poor. It is also termed “St. John’s Bread,” owing to the tradition that John the Baptist used its fruit in the desert. Quantities of the pods are imported into England under the name of locust beans, and used as food for horses (Luke 15:16).
Carob tree (Ceratonia siliqua) with fruit.