The spelling of the word "haddest relation" can be confusing, but it can be broken down using IPA phonetic transcription. The first syllable is pronounced as "hæd" with a short "a" sound, followed by "əst" representing the suffix "-est" indicating the superlative form of the verb "have". The second half of the word, "riːˈleɪʃən" is pronounced as "ree-lay-shun", representing the noun form of "relationship". Altogether, "haddest relation" means having the best relationship or being most related to someone or something.
The phrase "haddest relation" does not have a readily identifiable etymology as it appears to be a combination of two separate words: "haddest" and "relation". However, it is worth noting that "haddest" is an archaic form of the verb "have" in its second person singular past tense form. The term "relation" typically refers to the way in which things, people, or events are connected or related to each other. If you are referring to a specific context or usage of this phrase, providing more information might help in determining its precise origin.