身體撐不住
最具體的一支，也是核心畫面本身：撐不住的是一個人的身體，而且已經撐不住很久了。
adjective · C1
Weak or ill over a long period of time, so that ordinary things become hard to do. It is most often said about people who are old.
體弱多病的；（年老）虛弱的
核心畫面
One way to hold infirm: something that is supposed to hold steady does not hold. Picture a person who reaches for the wall on the way to the kitchen. The legs are still there, but they cannot be counted on any more. Move that picture off the body and you get the rest of the word. A will that keeps shifting, ground that may give way under an argument, a claim whose support has just been .
可以想成：本來應該撐住的東西，撐不住了。畫面是一個人走去廚房時，要扶著牆。腿還在，但已經不能指望了。把這個畫面從身體…更多收起
可以想成：本來應該撐住的東西，撐不住了。畫面是一個人走去廚房時，要扶著牆。腿還在，但已經不能指望了。把這個畫面從身體上移開，其餘的用法就出來了。一直在動搖的決心、一個論點底下隨時會塌的地基、一個支撐剛被抽掉的說法。四種用法看起來差很多，共用的其實是同一件事：不牢固。From the word’s history
The packet's source traces the adjective through Middle English infirme to Latin infirmus, glossed there as weak or feeble, and the verb to Latin infirmare from the same infirmus. So the body sense and the verb are one root, not two.
來源把形容詞一路追到中古英文 infirme，再到拉丁文 infirmus，並把 infirmus 解作「虛弱的、無力的」；動詞則來自同一個 infirmus 變出來的 īnfirmāre。所以身體那一支和動詞那一支同根，不是兩條線。
Wiktionary entries supplied in this packet (kaikki:3f6f69a190036ae4:1109801079:9979 and :1109811058:4917): 'from Latin infirmus (weak, feeble)'; 'The verb is from Latin īnfirmāre, from īnfirmus'
Two branches
心志或根基不牢
把「撐不住」從身體移到看不見的東西上：決心、判斷，還有一個說法底下的地基。
adjective · C2
Not firm or steady — used about a person's will or judgment, or about ground, reasons or ideas that something rests on but that will not hold.
不堅定的；不穩固的