The spelling "haddest hunch" may seem peculiar to modern English speakers, but it was actually a valid form of the past tense of the verb "to have" in Middle English. The word "haddest" is pronounced /ˈhædɪst/, with the emphasis on the first syllable and a short "a" sound in the second syllable. "Hunch" is pronounced /hʌntʃ/, with a short "u" sound and a soft "ch" sound at the end. So, "haddest hunch" would be pronounced something like /ˈhædɪst ˈhʌntʃ/.
The phrase "haddest hunch" does not have a specific etymology because it is not a recognized word or phrase in the English language. It appears to be a combination of two separate words: "haddest" and "hunch".
"Haddest" is the archaic second-person singular past tense and subjunctive mood of the verb "have" in Middle English. It was used to denote possession or ownership in older forms of English.
"Hunch", on the other hand, is a modern English word derived from the Old French word "haunce" which meant a push or jolt. Over time, it came to be used as a noun to refer to a gut feeling, an intuitive sense, or a premonition about something.