Put one figure in the middle: the person who buys. Everything this word can mean is a different answer to the question of what we do with that figure. Build a whole way of living around them and you get the buying culture. Argue that the economy runs on them and you get the economic theory. Decide they need defending and you get the protection movement. Same person at the centre, three different things done about them — which is why one word can sound like a complaint in one sentence and like a proud achievement in the next.
The Wiktionary entry builds the word from consume, which goes back through Old French to Latin consumere, and from there to consumer plus the ending -ism. The ending is what makes it big: -ism turns a role into a whole system built around that role.
Wiktionary 的詞源把這個字拆成 consume（來自拉丁文 cōnsūmō，經古法文進入英文）→ consumer → 再加 -ism。關鍵在最後那個字尾：-ism 把一個角色放大成一整套圍著這個角色轉的體系，所以這個字談的從來不是一次購物。
Wiktionary (kaikki:3f6f69a190036ae4:1340239648:25747), etymology_text supplied in the evidence packet
Two branches
把「多買」當成好事的想法
這一支把中間那個人看成「應該多買的人」。差別只在說話的人站哪裡：站在批評的位置，就是消費文化；站在分析的位置，就是經濟主張。
noun · C1
The belief that buying and using a lot of goods and services is a good thing, together with the way of living that goes with it. The word is usually used by people who think this is a problem.
消費主義
站在買東西的人那一邊
同樣以買東西的人為中心，但看法翻了過來：他不是該多買的人，而是比較弱勢、需要有人保護的一方。
noun · C1
Work done to protect the people who buy things — for example by acting against unfair prices, advertising that is not true, and unsafe products, and by making sure buyers are given clear information.
消費者保護運動