What does «مِرْدَاةً طَحُونًا» reveal in verse 33?

ʿAmr ibn Kulthūm: Address to Abā Hind, Tribal Pride and the Mill of War (Verses 23–38)

• Sweetmeats were served to guests
• A mill is being taken home
• The apparent hospitality is actually a crushing blow
• A wall is being built of stones