apple
檎 centers on the apple fruit. It is used specifically for apples, often in compound words.
檎 combines 木 (tree) with 禽, which likely contributes the sound. The character was created to represent the apple tree or its fruit.
The tree 木 on the left bears the fruit of the right side 禽, which looks like a bird pecking at an apple. Picture an apple tree with a bird-shaped fruit.
For キン, imagine a king apple: the biggest, shiniest apple on the tree. King -> キン, and the apple is fit for royalty.
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apple (fruit)
apple sold during the winter; winter apple
Chinese apple (Malus asiatica)
apple
apple juice
wooly apple aphid (Eriosoma lanigerum)
channeled apple snail (Pomacea canaliculata); golden apple snail
apple (Malus domestica)