The spelling of the word "haddest job" is based on Old English grammar rules, specifically the second person singular form of the past tense verb "have." The word "haddest" is pronounced /ˈhædɪst/ with the stress on the first syllable. The phonetic transcription shows that the word is pronounced with a short a vowel sound followed by the consonant /d/ and the suffix /ɪst/ denoting the second person singular. The compound word "haddest job" means you had the most difficult task.