stayed > remained; desisted [from starting her journey] gan > did

2 "O, you most ancient grandmother of all, 3 More old than Jove, whom you at first did breed, 4 Or that great house of gods celestial,

gods celestial > (The Olympian gods, over whom Jove reigned supreme; see Myth. 3.12)

5 Which was begotten in Demogorgon's hall,

Demogorgon > (A primordial enchanter commanding the underworld (DGDG 1.1); Chaos. Progenitor of all the gods. See also 101.37:8, 402.47:7)

6 And saw the secrets of the world unmade,

unmade > [in its chaotic or primeval state; see PL 2.890-6]

7 Why suffered you your nephews dear to fall

suffered > allowed nephews > grandsons; descendants [Sansfoy and Sansjoy]

8 With Elfin sword, most shamefully betrayed? 9 Lo, where the stout Sansjoy does sleep in deadly shade!