核心畫面
Think of ordinarily as the adjective ordinary opened out into an adverb: in the ordinary way. What changes between the two senses is how much of the sentence the phrase is laid over. Held close to the verb it covers the action, so he was dressed ordinarily is about the manner. Stretched over the whole sentence it covers the event as a whole, so Ordinarily he walks to work is about the pattern.
可以想成把形容詞 ordinary 攤開成一個副詞：「照普通的樣子」。兩個意思差在這句話蓋住多大的範圍。貼著動詞放，…更多收起
可以想成把形容詞 ordinary 攤開成一個副詞：「照普通的樣子」。兩個意思差在這句話蓋住多大的範圍。貼著動詞放，蓋住的就是那個動作，he was dressed ordinarily 講的是穿的樣子。往外拉到整句話，蓋住的就是整件事，Ordinarily he walks to work 講的是平常的習慣。位置常常就是判斷的線索。From the word’s history
Wiktionary analyses ordinarily as ordinary + -ly, the ordinary adverb-forming ending that reaches English through Middle English.
Wiktionary 把 ordinarily 拆成 ordinary 加上 -ly。-ly 是英文最常見的副詞字尾，經由中古英文進入現代英文。所以這個字的字面就是「照 ordinary 的樣子」。
Wiktionary entry 'ordinarily' (packet source_ref kaikki:3f6f69a190036ae4:825146680)