Think of something thin enough that you handle it carefully — a cup you would not leave at the edge of the table. Frailty can be pictured as that quality: not simply low in strength, but likely to give way if anything presses on it. English then lets the same picture cover a body and a character, so the word that describes a person who must not fall also describes a person who cannot hold out.
From the word’s history
Wiktionary traces frailty through Middle English frelete and Old French fraileté to Latin fragilitas, and notes it is a doublet of fragility — literally the state of being breakable, which is the picture the modern word still carries.
Wiktionary 記載 frailty 經中古英語 frelete、古法文 fraileté 來自拉丁文 fragilitās，並指出它與 fragility 同源。字面就是「易碎的狀態」，而這正是今天這個字還在用的畫面。
Wiktionary entry 'frailty' (kaikki:3f6f69a190036ae4:1240227975), supplied in the evidence packet.
登入就可以看每一支怎麼連回核心畫面。