肥皂搓出來的泡沫
這一家就是核心畫面本身，只是分成三個角度看：那團泡沫（名詞）、泡沫怎麼冒出來（不及物動詞）、泡沫被抹到哪裡（及物動詞）。
noun · B2
The thick white foam that soap or shampoo makes when you rub it together with water.
泡沫
核心畫面
Think of a bar of soap in wet hands. You rub, and rub, and a thick white foam rises up and covers whatever you are washing. That foam is a lather, and the key part of the picture is that it does not pour out ready-made — it is worked up by rubbing. English keeps that same picture outside the bathroom. A horse that has run hard is rubbed by its own harness until its sweat turns to white foam, and that is called lather too. From there the picture moves to people: someone who has got themselves worked up over something is said to be in a lather.
lather 可以想成這樣一個畫面：手是濕的，肥皂在手裡搓啊搓，一層厚厚的白泡沫慢慢冒起來，蓋住你正在洗的東西。畫面…更多收起
lather 可以想成這樣一個畫面：手是濕的，肥皂在手裡搓啊搓，一層厚厚的白泡沫慢慢冒起來，蓋住你正在洗的東西。畫面的重點不在泡沫本身，而在那個「搓」——泡沫不是倒出來的，是摩擦和力氣弄出來的。這個畫面英文沒有留在浴室裡。馬跑久了流汗，被馬鞍和韁繩不斷摩擦，汗也被搓成一層白沫，看起來一樣，就沿用同一個字。再往前一步，人急起來、坐立難安的樣子也像那匹冒白沫的馬，於是有了 in a lather 這種說法。From the word’s history
Wiktionary traces the noun to Old English lēaþor, a substance used for washing, and on back to a Proto-Indo-European root meaning to wash or bathe. The verb comes from the matching Old English verb līeþran, to soap or wash. So the washing picture sits in the word from the very start.
Wiktionary 記載，名詞 lather 來自古英文 lēaþor，指一種拿來洗東西的鹼，再往前可追到印歐語根 *lewh₃-（洗、沐浴）；動詞則來自對應的古英文動詞 līeþran（塗肥皂、洗）。也就是說，「洗」這個畫面從一開始就在這個字裡面，今天的泡沫義是它最直接的延續。
Wiktionary (kaikki extract kaikki:3f6f69a190036ae4:610730709 noun ety1; :610755808 verb ety2), entry 'lather'
Three branches
馬流汗結成的白沫
馬跑久了，汗和皮膚上的油脂被馬鞍、韁繩不斷摩擦，搓成一層白泡沫，看起來跟肥皂泡幾乎一樣。核心畫面沒有改變，只是換了場景，也換了一種「搓」的力量：這次不是手，是牠自己的裝備和動作。
noun · C1
The white foam that forms on a horse's coat when it has been sweating hard, for example after running a long way.
（馬的）汗沫
人焦躁到像冒白沫的馬
從第二家再走一步：馬跑到冒白沫的樣子被借來形容人。要注意的是，這一步只發生在固定片語裡，lather 單獨用並沒有「焦慮」的意思。
noun · C1
If someone is in a lather, they are very worried, upset or excited about something, and it shows.
焦躁不安