鞋帶本身，以及像鞋帶一樣細長的東西
這一家就是字面的那條繩子，加上借了它形狀的用法。其他家都是從這裡走出去的。
noun · B1
A shoelace: the thin cord that goes through the holes of a shoe and is tied to hold the shoe on your foot. This word is used mainly in American English.
鞋帶
核心畫面
Think of one lying on a table: long, thin, narrow, and worth almost nothing. Every other use of shoestring seems to borrow one feature of that little cord. Some borrow its shape — a strip of land, a thin-cut fry. One borrows its position, down at shoe level, for a catch made just above the grass. And the best-known ones borrow its cheapness: money so thin there is nothing spare.
可以想成一條攤在桌上的鞋帶：又細、又長、又不值錢。shoestring 的每個用法，都像是從這條繩子身上借走了一個特…更多收起
可以想成一條攤在桌上的鞋帶：又細、又長、又不值錢。shoestring 的每個用法，都像是從這條繩子身上借走了一個特點。有的借形狀，像細長的一塊地、切得很細的薯條。有的借位置，球低到鞋帶那裡，就成了貼地的接殺。最有名的那組借的是它的便宜——錢少到像一條繩子，剛好夠用，一點都不剩。把這條繩子記在腦子裡，這幾個看起來不相干的意思就連起來了。From the word’s history
The noun is formed from shoe + string, so the word literally names the string of a shoe. That plain compound is also the picture the figurative uses run on.
這個名詞由 shoe（鞋）加 string（細繩）組成，字面就是「鞋子的繩」。來源明確說明了這個組成方式。比喻用法用的也正是這個字面畫面。
Wiktionary entry for shoestring (packet etymology_text): "The noun is derived from shoe + string."
Two branches
少得可憐的錢
這一家借的不是形狀，是那條繩子的「不值錢」。資源細到剛好夠綁起來，再多就沒有了。
noun · B2
If you do something on a shoestring, you do it with very little money — just enough to get it done, with nothing spare.
用極少的錢（做成某事）