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.
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 (kaikki extract) entry for patchy: From patch + -y. source_ref kaikki:3f6f69a190036ae4:655451472:6995
Two branches
分布一塊一塊的
這一組就是核心畫面本身：東西只出現在某些地方，中間是空的。
adjective · B2
Happening or existing in some places but not in others, so that it is spread out unevenly with gaps in between. Often used about weather such as fog, rain or cloud, and about things like grass, paint or a phone signal that cover an area unevenly.
零星的、一塊一塊的
品質與內容的不均
把同一張「有塊有洞」的版面，從地面搬到內容和品質上；空隙就變成缺掉的知識，或表現下滑的那幾段。
adjective · B2
Not complete or thorough enough to be useful, because whole parts of it are missing. Used about knowledge, evidence, records, notes and other things you expect to cover a subject fully.
不完整的、有缺口的