Start with broil: strong heat beating straight down onto food from close above. A broiler is whatever that heat has to do with — the hot bar at the top of the oven that makes it, or the young bird raised to go under it.
Broil + -er, where -er is the suffix that names the doer; for the chickens it works the other way and names the one the action is done to. That single split is exactly why the word covers both a part of a cooker and a farm bird.
字面是 broil 加 -er。-er 通常指「做這件事的那一個」，但用在雞身上時方向反過來，指「被這樣處理的那一個」。這個字尾的兩種方向，正好說明為什麼同一個字可以同時是烤箱裡的一區，也是農場裡的一隻雞。
Wiktionary entry 'broiler', etymology_text supplied in this packet (source_ref kaikki:3f6f69a190036ae4:1091764448)
Two branches
製造那把火的那一個
-er 最常見的方向：做動作的那一個。
noun · B2
The part of an oven or stove that sends strong heat straight down onto food from just above it, used to brown food or cook it fast. This is the American English name; British English calls the same thing a grill.
上火炙烤區
被送去火底下的那一個
一樣從 broil 來，只是 -er 指的對象換了一邊：從做動作的，變成承受動作的。
noun · B2
A chicken raised for its meat rather than for its eggs, especially a young bird of about six to ten weeks old. It is often used in front of another noun: broiler chicken, broiler farm.
肉雞