Picture someone lifting the lid of a box and seeing every tool they own lying there, sorted, clean and within reach. Two things make that picture work, and both of them travel into the other uses: the tools were gathered in advance by somebody who knew what would be needed, and they are all in one place, so you can take out whichever one this job asks for. Whenever English calls something a toolbox, it is saying that about it.
可以想成有人掀開一個箱子的蓋子，裡面所有工具都排好在那裡，乾淨、伸手就拿得到。這個畫面有兩個重點，而且兩個都被帶進了其他用法。第一，工具是有人事先收集好的。第二，它們全在同一個地方，需要哪一件就拿哪一件。英文只要把某樣東西叫 toolbox，講的多半就是這兩件事。
From the word’s history
Wiktionary gives the word as tool + box, so the compound says exactly what it holds.
來源寫的是 tool 加 box，也就是「裝工具的箱子」。字面和核心畫面完全對得上，不需要繞路。
Wiktionary entry for toolbox, supplied in this batch's evidence packet: From tool + box.
登入就可以看每一支怎麼連回核心畫面。