One big, fast swallow. The throat opens, a whole mouthful goes straight down, and the movement is large enough for other people to see and often to hear. Everything else the word does comes from changing what goes down. Usually it is drink or food. Sometimes it is air, taken in as if you could drink it. And sometimes nothing goes down at all — the throat still moves, and that empty swallow is what fear and nerves look like from the outside. Because the action is visible, gulp is both something you do and something other people read.
From the word’s history
Wiktionary traces gulp to Middle English gulpen, probably taken from West Flemish or Middle Dutch gulpen; the origin is described as uncertain, and one suggestion there is that the word simply imitates the sound. If that suggestion is right, it sits well with the modern word, which still names a swallow you can hear.
依照維基詞典的說明，gulp 來自中古英語 gulpen，可能是從西佛蘭德語或中古荷蘭語的 gulpen 借來的，來源本身標為不確定。那裡也提到一種可能：這個字本來就是在模仿聲音。如果這個說法成立，它跟今天的用法就對得上——gulp 指的一直是聽得見的那一吞。
Wiktionary 'gulp' etymology section, as supplied in this packet (source_ref kaikki:3f6f69a190036ae4). Origin explicitly marked uncertain there; the imitative account is one suggestion, not a settled fact.
登入就可以看每一支怎麼連回核心畫面。