look is a prefix of Thai word for calling fruits as the tree’s offspring , so (look)+(fruits’ name) is basically…
the word “look” (ลูก) means child or offspring and is commonly used before fruit names to mean the fruit of a tree. so lookpeach literally means “the child of a peach tree,” which is just how thai refers to a peach. it’s not a separate concept or slang, just a direct romanization of the thai full name for the fruit, and it shows a linguistic habit of describing fruits as a tree’s offspring rather than having extra cultural symbolism.
i think the one you're referring to is about mhok and rome's backstory when they were in highschool. later thee and mhok moved to thailand for business and after seven years is what we're seeing in this drama. i will attach the link for that book below