What is the meaning of "al-fūm" in this āyah?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means wheat. [Ibn ʿAbbās, al-Suddī, al-Ḥasan, Abū Mālik] Al-Farrāʾ stated that it is an ancient usage. Those who used it would say in their dialect: "fawwimū lanā", meaning: "bake for us."

1. It means garlic. Ibn Masʿūd and Ubayy ibn Kaʿb read the verse "wa thūmihā" (Thūm is garlic). Al-Farrāʾ favored this interpretation on the grounds garlic is similar to the other items mentioned in the verse. It is common for the Arabs to swap faʾ and thaʾ in many words. [Mujāhid, al-Rabīʿ ibn Anas, Muqātil, al-Kisāʾī, al-Naḍr ibn Shumayl, Ibn Qutaybah]
2. It means grains. [Ibn Qutaybah, al-Zajjāj]