The phrase "hadst someone pegged" is commonly used to mean that someone has accurately judged or assessed another person. The word "hadst" is an archaic form of the word "had," which is the past tense of the verb "have." The IPA phonetic transcription of "hadst" is /hædst/, with the "st" at the end signifying the second person singular past tense. This spelling is uncommon in modern English, and the word is often replaced with "had" or a more informal variation, such as "had someone figured out."