You can think of lacquer as a wet layer that you put on a surface and then wait for. While it is wet it is nothing much. Once it dries it becomes a thin hard skin that holds the surface still and throws back the light. Everything the word does grows out of that one moment of setting: the liquid in the tin, the act of brushing it on, and even the spray that freezes a for the evening.
Wiktionary traces lacquer through French lacque and Portuguese laca ('gum lac') back through Persian lāk and Hindi lākh to Sanskrit lākṣā, and calls it a doublet of lac. The older meaning is a resin, which sits close to the modern picture of a sticky liquid that hardens into a shine.
Wiktionary 的線索是：梵文 lākṣā → 印地語 lākh → 波斯語 lāk → 葡萄牙語 laca（樹脂）→ 法語 lacque → 英文，並指出它和 lac 是雙生字。早期指的是樹脂。那團會凝固的樹脂，和今天「乾了會硬、會亮」的畫面剛好接得上。
Wiktionary entry for 'lacquer' supplied in this packet (kaikki:3f6f69a190036ae4:928112169:16956)
Two branches
刷上去、乾了變硬變亮的那一層
這一組就是核心畫面本身：材料，以及把材料塗上去的動作。
noun · C1
A liquid that is painted or sprayed onto wood or metal and then dries into a hard, shiny surface. It can come from the sap of certain trees, or it can be made from man-made materials mixed into a liquid.
亮漆
噴在頭髮上、讓髮型不動的那種
把同樣的畫面換個對象：噴上去是濕的，乾了就把表面固定住，只是這次的表面是頭髮。來源把這兩個用法都標成 old-fashioned，今天大多說 hairspray／spray。
noun · C2
Hairspray: a liquid sprayed onto hair to hold it in place. The source marks this use as old-fashioned, and most speakers now say hairspray.
髮膠（舊式說法）