You can think of banner as one piece of cloth lifted on a pole where a crowd can see it. The cloth carries a mark: a colour, a family sign, a name, a sentence. Whoever stands under it is saying, without speaking, this is what I belong to. Almost everything else the word does keeps that shape — something wide and flat, put up in front of people, telling them which side you are on.
From the word’s history
Recorded as coming from Middle English baner, from Old French baniere, of Germanic origin, and the same source note links it to band. A band is something that ties people together, and a cloth on a pole is exactly the sign that a group is tied together — which is why the word later names the group as easily as the cloth.
資料記載 banner 來自中古英語 baner，再往前是古法語 baniere，源頭是日耳曼語，並註明與 band 同源。band 是把東西或人綁在一起的帶子。一塊布升在桿子上，正好就是「這群人綁在一起」的記號。所以這個字後來既可以指那塊布，也可以指旗下的那群人。
Wiktionary (kaikki extract, source_ref kaikki:3f6f69a190036ae4:630055029), banner etymology 1: From Middle English baner, from Old French baniere (Modern bannière), of Germanic origin. More at band.
登入就可以看每一支怎麼連回核心畫面。