The Talmud notes that carob pods alone nourished the poor Rabbi Hanina ben Dosa from Shabbat to Shabbat. (Ta’anit, 24b) The famous Honi Hamaagal story about planting for future generations centers on a carob plant. (Ta’anit, 23a). Carob’s appearance in other Middle Eastern based religions extends to Islam. During Ramadan carob juices are drunk. In addition, in Christian sources, the Book of Matthew (3:4) claims that John the Baptist ate carob in the desert, thus explaining its English denotation as St. John’s Bread. Perhaps this association puts carob on Easter and Lent menus.As for Matthew 3:4, my understanding is that when it says John ate locusts, it means locusts. For my part I would be happier if it meant carobs. More on that here and here.
More on the holiday of Tu B'Shevat (coming this weekened) here.