The spelling of the word "haddest foundation" can be broken down through its pronunciation, using phonetic transcription. The word "haddest" is pronounced /ˈhædəst/ which translates to "had-uhst." This is the past tense form of "have" in the second-person singular form. Meanwhile, "foundation" is pronounced /faʊnˈdeɪʃən/, which translates to "fowndey-shuhn." It means the underlying basis or structure of something. Together, "haddest foundation" means "you had the foundation," referring to someone having established something solid as a basis.