You can picture discouragement as what is left when someone's courage has been taken out of them. The same word can point at the empty feeling inside the person, at the act of taking the courage out, or at the thing that did the taking — one picture, looked at from three places.
From the word’s history
The word is discourage + -ment, and discourage still shows courage inside it with dis- in front. Read that way, the noun is 'the taking away of courage' — and English lets that name the feeling, the act, or the cause.
字是 discourage 加 -ment 來的，discourage 裡面還看得到 courage（勇氣），前面的 dis- 帶有「拿掉」的意思。這樣讀下來，這個名詞就是「勇氣被拿走」這件事；英文再讓它同時指那個感覺、那個動作，和那個原因。
Wiktionary, entry 'discouragement' etymology tree (source_ref kaikki:3f6f69a190036ae4:1269218344:7299), supplied in the evidence packet
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