頭先下去（字面）
這一族就是核心畫面本身，沒有任何比喻：一個身體往前或往下，頭在最前面。副詞和形容詞兩種形狀描述的是同一件事，只是一個掛在動詞後面，一個放在名詞前面。
r · B2
With your head going first and the rest of your body following after it.
頭先著地地、頭朝前地
核心畫面
One way to hold this word: your head has gone out in front of you and the rest of you is following, whether you like it or not. Once the head is leading, there is no foot on the ground to push back with — no brake, no turn, no second look. Every use of headlong keeps some part of that. Sometimes it is a real body falling. Sometimes it is a person moving too fast to see what is ahead. Sometimes nothing moves at all and it is a decision that has already left without you.
可以想成「頭已經衝到前面，身體被拖著跟上」。頭一旦跑在前面，就沒有一隻腳能踩住地了。沒有煞車，沒辦法轉彎，也來不及再…更多收起
可以想成「頭已經衝到前面，身體被拖著跟上」。頭一旦跑在前面，就沒有一隻腳能踩住地了。沒有煞車，沒辦法轉彎，也來不及再看一眼。這個字的每一種用法都留著這個畫面的一部分。有時候是真的有人往前跌。有時候是有人跑太快，看不見前面。有時候什麼都沒有動，是一個決定已經自己衝出去了。From the word’s history
The packet's source entry traces headlong to Middle English hedlong, an alteration of hedling / heedling / hevedlynge, later assimilated to the word long. So the second half was not originally long at all — it was an old adverb ending. The weight of the word has always sat on head, which is exactly where the picture above sits.
證據裡的來源把 headlong 追到中古英文 hedlong，說它是 hedling／heedling／hevedlynge 的變體，後來被同化成看起來像 long 的樣子。所以後半本來根本不是「長」，而是一個舊的副詞字尾。這個字的重量一直都在 head 上，剛好就是上面那個畫面的重點。
Wiktionary (kaikki extract supplied in this packet, source_ref kaikki:3f6f69a190036ae4:1111420497:20273): "From Middle English hedlong, alteration of hedling, heedling, hevedlynge ('headlong'), assimilated to long."
Three branches
衝太快、來不及看路
畫面從「姿勢」換成「速度」。人沒有在跌倒，但一樣失去了煞車：跑得太快，前面有什麼都來不及看。頭在前面的那個「停不住」被保留下來，往前跌的動作被拿掉了。
r · B2
Moving very fast and without looking where you are going, so that you cannot easily stop or change direction.
橫衝直撞地、不看路地
想都沒想就一頭栽進去
這一族什麼都沒有在動。往前跌的畫面被搬到「做決定」上：你已經投進去了，回不了頭。它只以 rush／plunge headlong into something 這個固定形狀出現，所以在我們的字典裡被標成片語，而不是這個字單獨的意思。
r · C1
If you rush or plunge headlong into something, you start doing it very fast, before you have thought it through.
貿然投入、一頭栽進去