The spelling of the word "hadst propensity" can be a little challenging due to its archaic language and irregular pronunciation. According to the International Phonetic Alphabet (IPA), "hadst" is pronounced as /hædst/, which makes use of the voiced dental fricative "th" sound. On the other hand, "propensity" is pronounced as /prəˈpɛnsəti/, which uses the schwa vowel sound and the voiceless alveolar affricate "t" sound. Despite its unusual spelling, "hadst propensity" simply means "you had a tendency or inclination."
The phrase "hadst propensity" is not a common word or phrase that can be found in the English language. "Propensity" is a noun that means a natural inclination or tendency, while "hadst" is an archaic form of the verb "have" used in the second person singular past tense.
If someone used the phrase "hadst propensity", it would likely be an archaic or poetic form of expressing that you had a natural inclination or tendency towards something in the past. However, it is important to note that this phrase is not commonly used in modern English and does not have a widely known etymology.