Odd means not matching the rest. Add -ity and English can talk about that not-matching as a thing you can point at. Sometimes you point at the strangeness itself — the oddity of a house where every window is a different size. Sometimes you point at whatever is carrying it — the house, the coin, the who reads dictionaries for fun. One word, and you choose where it lands: on the quality, or on the one thing standing apart from everything around it.
From the word’s history
The packet's Wiktionary entry gives 'From odd + -ity', with -ity arriving through Latin -itas, Old French -ite and Middle English -ite. A suffix like that normally makes a quality noun, which is exactly the second sense; English then also lets the same word name whatever has the quality, which is the first.
證據包裡的字源是 odd 加上 -ity，而 -ity 經拉丁文 -itās、古法文 -ite、中古英文 -ite 進入英文。這種字尾本來是把形容詞變成一個性質名詞，也就是第二個意思。英文接著又讓同一個字去指「帶著這個性質的那一個」，於是有了第一個意思。
Wiktionary entry supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:576400823), etymology_text: 'From odd + -ity.'
登入就可以看每一支怎麼連回核心畫面。