What did God tell Hosea to name Gomer's daughter?

Answer: Lo-ruhamah

God said, "Name her Lo-ruhamah, for I will no longer have compassion on the house of Israel" (KJV: "no more have mercy").

“Gomer again conceived and gave birth to a daughter, and the LORD said to Hosea, “Name her Lo-ruhamah, for I will no longer have compassion on the house of Israel, that I should ever forgive them.”— Hosea 1:6 (BSB)