A popular saying in various fields of halachah (Jewish law) is “frailty/feebleness descended upon humanity” (״ירדה חולשה לעולם״). This is perhaps most known in the area of fasting where some authorities exercise some leniency in certain situations. A simple Google or Sefaria search yields some results, the earliest of which I’ve seen is Chaye Adam. What is the earliest application or usage of this term in the field of halachah? (Disclaimer: I don’t know if CA is the earliest.)
Unlike this question (and this question; HT/Dr. Shmuel) which treats a similar expression that relates more specifically to spiritual parameters, almost theosophical in nature, I am asking where the aforementioned saying is directly applied to and influences any given halachah.