KanjiJLPT N1
Armor

armor, high (voice), A grade, first class, former, instep, carapace

Mnemonic

Pictograph of a shield of armor.

Details

The keyword for 甲 is armor. This kanji originally depicted a suit of protective covering worn in battle, resembling a shell or hard outer casing. By extension, it came to signify anything that ranks first or is of the highest grade, much like the top-tier protection that armor provides. It is also used as the first in a traditional ordering system (similar to "A" in English), and can refer to the shell of a turtle or the back of the hand.
On'yomi
こう、かん
Kun'yomi
きのえ