shoal: English has two distinct words shoal. ‘Shallow area’ [16] is descended from the Old English adjective sceald ‘shallow’, which in turn came from prehistoric Germanic *skaldaz. (English shallow [15] is related, although it is not clear precisely how.) Shoal of fish [16] is simply a reborrowing of Middle Dutch schōle, which had earlier been taken over as school. => school[shoal etymology, shoal origin, 英语词源]