Something you were never going to keep. Picture a cup at a food stall: thin, cheap, made in a factory by the thousand, and already on its way to the bin before you have finished drinking. The point is not that it broke. The point is that throwing it out was the plan from the start, and that is why nobody minds. Every use of the word can be read as that same cup wearing a different shape — a flyer pushed into your hand, a remark tossed out at lunch, an account opened to ask one question. Each is light, each is meant to last a moment, and each is easy to let go of.
From the word’s history
The source says throwaway is formed straight from the phrasal verb throw away. So the picture is not a guess about the word's history — the action is sitting inside the word, and the two halves still say what they say.
資料說 throwaway 就是直接從動詞片語 throw away（丟掉）變來的。所以上面那個畫面不是猜的：那個動作本來就在字裡面，兩個部分現在讀起來還是原來的意思。
Wiktionary entries for throwaway, adjective and noun (source_refs kaikki:3f6f69a190036ae4:1466630480 and :1466637430): "Deverbal from throw away."
登入就可以看每一支怎麼連回核心畫面。