這個拼法底下其實是2個不同的字，意思沒有關係， 只是長得一樣。下面分開列出來。跳到 魚鰓 · 及耳（四分之一品脫）
唸法不同同樣的拼法，這個字的唸法跟另一個不一樣。/ɡɪl/
Hold a fish and lift the flap behind its head. Underneath are rows of thin red folds, packed close together, opening and closing as water passes over them. That is the picture the word carries: many thin blades side by side, high up on the sides of a body. Turn a mushroom over and you find the same shape, so it borrows the same name. And because the folds sit near the top of the fish, filling something right up to that line became a way of saying completely full.
From Middle English gille, of North Germanic origin, related to Danish gælle and Swedish gäl; the older Norse word has also been linked to a root meaning 'lips' or 'jaw', which fits the opening-and-closing picture.
來自中古英文 gille，源頭是北日耳曼語，跟丹麥文 gælle、瑞典文 gäl 同一家人；更早的古諾斯語詞也被連到「嘴唇、下顎」的字根，正好對上那個一張一合的畫面。
Wiktionary etymology_text supplied in this packet for gill, etymology 1 (kaikki:3f6f69a190036ae4:804484453)
Two branches
魚頭兩側的薄褶，以及借用它的形狀
這一支就是核心畫面本身，以及外形太像而直接沿用這個名字的東西。
noun · B1
One of the openings on each side of a fish's head, covered by a flap and lined with thin red folds, through which the fish breathes by taking oxygen out of the water; also found on other water animals, and nearly always used in the plural.
魚鰓
滿到那條線：to the gills
鰓長在魚身偏上的地方，所以「裝到鰓」等於裝到最上緣。這一支是把位置的畫面拿來講份量。
noun · B2
If a place, a container, or a person is packed, full, stuffed, or crammed to the gills, it is completely full, with no room left at all.
塞得滿滿的、擠爆了
A second word, same spelling
唸法不同同樣的拼法，這個字的唸法跟另一個不一樣。/dʒɪl/
A different word that happens to be spelled the same, and is even said differently: /dʒɪl/, like the name Jill. Picture a small pouring on a kitchen shelf, the kind that holds about a teacup of liquid. The vessel came first and the amount took its name from it, the way a cup became a measurement. That amount settled at a of a pint, so four of them fill a pint.
From Middle English gille, from Old French gille 'a wine measure', from Medieval Latin gillo 'earthenware jar' — the jar, then the amount it held.
來自中古英文 gille，再往上是古法文 gille「一種酒的量器」，源頭是中世紀拉丁文 gillo「陶罐」——先是那個罐子，然後才是罐子裝的份量。
Wiktionary etymology_text supplied in this packet for gill, etymology 2 (kaikki:3f6f69a190036ae4:804538429)