One way to hold patchy: look down at a field after a dry summer. Green in one place, bare soil in the next, green again further on. Nothing is spread evenly; it arrives in separate pieces with gaps between them. Every use of the word keeps that layout — some parts full, some parts empty — whether the field is a road full of fog, a subject you half know, or a show that is strong for ten minutes and flat for the next ten.
patchy 可以想成乾了一整個夏天的草地：這裡一片綠，旁邊一塊光禿，再過去又有草。東西不是平均鋪滿的，而是一塊一塊出現，中間留著空隙。三個用法都保留這個版面：有的地方滿、有的地方空。差別只在那塊「地」是什麼——可能是一條起霧的路，可能是你只學了一半的語言，也可能是一場前半精采、後半拖戲的演出。
From the word’s history
Wiktionary gives patchy as patch + -y, that is, having patches. The modern picture of separate areas with gaps between them sits directly on that literal reading.
Wiktionary 記錄 patchy 來自 patch（補丁、一塊區域）加上 -y（帶有…性質的），字面就是「有很多塊的」。今天那個「一塊有、一塊沒有」的畫面，正好就建立在這個字面意思上。
Wiktionary, "patchy"
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