Albert Barnes Commentary 2 Kings 21:18

"And Manasseh slept with his fathers, and was buried in the garden of his own house, in the garden of Uzza: and Amon his son reigned in his stead." — 2 Kings 21:18 (ASV)

Was buried - The catacomb of David was probably full, and the later kings, from Ahaz downward, had to find a burial place elsewhere. Ahaz was buried in Jerusalem, but not in the sepulchres of the kings (2 Chronicles 28:27). Hezekiah found a resting place on the way that led up to David’s catacomb (2 Chronicles 32:33). Manasseh and Amon were buried in the garden of Uzza, a portion (apparently) of the royal palace garden, perhaps so named after its previous owner. Josiah was buried in his own sepulchre (2 Kings 23:30).

Amon his son - This name, which occurs only at this time and in the reign of the idolatrous Ahab (1 Kings 22:26), is identical in form with the Hebrew representative of the great Egyptian god, Amen or Amun (Nahum 3:8, margin); and it is therefore probable that Manasseh selected it and gave it to his son as a compliment to the Egyptians.