Think of a small family of elements that cannot leave anything alone. Put one of them next to a metal and it grabs on, and what you get is a salt — the salt on your table is exactly that. Everything the word does starts from that eager, grabbing gas. Seal a little of it inside a glass bulb with a hot wire, and the same gas keeps the wire burning white and bright, which is why a lamp ends up wearing the name of a chemical.
Coined in 1842 from Ancient Greek hals, salt, plus the ending -gen, producing: literally the salt-makers. The name records the behaviour, not the substance, which is why the group is defined by how eagerly it combines.
1842 年造的字：前半是希臘文的「鹽」，後半是「產生」，字面上就是「造鹽的那些」。這個名字記的是行為，不是外表。所以這一族真正的共同點不是長得像，而是「很容易結合」這件事。
Wiktionary etymology supplied in this packet (source_ref kaikki:3f6f69a190036ae4:727488460); coinage attributed there to Berzelius, 1842
Two branches
化學上的那一族元素
這一支就是核心畫面本身：那群很愛跟別人結合的元素。
noun · B2
One of a small group of closely related chemical elements — fluorine, chlorine, bromine, iodine, astatine, and the more recently named tennessine — which join with other elements very easily and form compounds, especially salts.
鹵素
生活裡的鹵素燈
把核心畫面裡的氣體封進燈泡，名字就跟著搬到燈上。這是一條命名上的連結：產品用材料的名字。
noun · B2
A very bright kind of electric light with halogen gas sealed inside the bulb. The word is used mostly before another noun, as in halogen lamp, halogen bulb or halogen oven, and sometimes on its own for the lamp itself.
鹵素燈