"haddest fun" is not a commonly used phrase in modern English, but it can be broken down phonetically as /ˈhæd.ɪst fʌn/. The first word, "haddest," is the archaic second-person singular form of "have." The second word, "fun," is a noun that refers to enjoyment or amusement. Together, the phrase means "you had the most enjoyment." While not commonly used today, it can still be found in older literature or when imitating older forms of English.
The phrase "haddest fun" appears to be a combination of two words: "haddest" and "fun".
The word "haddest" is the second person singular past tense of the verb "have" in Middle English. It is derived from the Old English word "hæfde", which means "had". In Middle English, verbs were inflected based on the subject pronoun and tense of the sentence, hence "haddest" is used for second person, singular, past tense.
The word "fun" originated in the late 17th century and is believed to have come from the adjective "funny", which initially meant "joking" or "humorous" in English. Over time, it evolved to be used as a noun to describe the experience of enjoyment or amusement.