Think of honour as something other people hand you and keep handing you: they respect your name, and they take your word as good. Dis- takes it back. So you can picture dishonour as that thing being returned or torn up. Which half is being torn up decides the sense. If it is the respect, a family or a uniform loses its good name. If it is your word, then a deal you made, or a that promised money, is simply not honoured. The two halves are the same idea seen from outside and from inside: what people think of you, and whether what you said can be relied on.
Wiktionary gives the word as from Old French deshonor, equivalent to dis- plus honour. The two parts are still visible in modern use, which is why both branches of the word can be read straight off honour.
來源記載：dishonour 出自古法語 deshonor，等於 dis- 加 honour。這兩個部件到今天還看得出來，所以這個字的兩條分支，都可以直接從 honour 反過來讀。
Wiktionary (kaikki extract in this packet), dishonour etymology_text, source_ref kaikki:3f6f69a190036ae4:1059123535
Two branches
名聲那一半：別人的敬重被收回
這一家撕掉的是「別人敬重你」那一半，所以受影響的通常不是一個人，而是一個名字：家族、制服、學校。
noun · C1
The loss of other people's respect, because someone has done something that is felt to be morally wrong or shameful. It is often felt to fall on a whole family, school, team, or country, not only on the person who acted.
恥辱、名譽掃地
承諾那一半：講好的不算數
這一家撕掉的是「你說的話算數」那一半。受詞從人變成東西：協議、合約、支票——都是把承諾寫下來的載體。
verb · C1
To refuse to do what you agreed or promised to do, for example by not keeping the terms of a contract, a deal, or a pay agreement.
不履行（協議、承諾）