Jamieson, Fausset and Brown on Isaiah 19:13

13. Noph--called also Moph; Greek, Memphis (Ho 9:6); on the western bank of the Nile, capital of Lower Egypt, second only to Thebes in all Egypt: residence of the kings, until the Ptolemies removed to Alexandria; the word means the "port of the good" [Plutarch]. The military caste probably ruled in it: "they also are deceived," in fancying their country secure from Assyrian invasion.

stay of ... tribes--rather, "corner-stone of her castes" [Maurer], that is, the princes, the two ruling castes, the priests and the warriors: image from a building which rests mainly on its corner-stones (see on Is 19:10; Is 28:16; Psa 118:22; Nu 24:17, Margin; Jud 20:2; 1Sa 14:28, Margin; Zec 10:4).