You can picture grouch as the low grumbling noise a person makes when something small has them — words half under the breath, and then again. Everything the word does can be seen growing out of that noise: the act of making it, the small thing it is aimed at, the mood it comes out of, and the person who is always making it.
From the word’s history
The packet's source entry traces grouch to Middle English grouchen, a variant of grucchen, meaning to complain, mumble or murmur. The mumbling is the oldest part of the picture, and it is still the part every modern use shares.
來源資料把 grouch 追到中古英語的 grouchen，它是 grucchen 的變體，意思是「抱怨、咕噥、低聲嘀咕」。可以想成：最早的畫面就是那個含在嘴裡的咕噥聲。今天四個用法，都還帶著那個聲音。
packet wiktionary etymology_text for grouch (source_ref kaikki:3f6f69a190036ae4:885788583)
登入就可以看每一支怎麼連回核心畫面。