So about halfway through season 2 we get these scenes.
These are called back to later, notably nine episodes later when Luz greets Amity as "Sweet Potato" shortly before they kiss on the mouth for the first time.
In the third season premiere, we see "Batatas," which is to say, the Spanish for sweet potatoes, being legible on a list of food items that is briefly visible when Luz's mom is going over her notes regarding which food items witches can and can't eat, and it has an "N" circled next to it suggesting that they're in the 'no' pile. Either sweet potatoes are unpalatable to witches, or they can't digest them properly.
Either way, the terms of affection that Amity and Luz sometimes use for each other refer to food that Amity can't eat.
I find that ironic.