甲
コウ, カン, カ, きのえ, かぶと, き, まさ, まさる

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

JLPT1 G7 S5 F1073

Originally, a depiction of objects being pressed down, suggesting "press down on objects in containing them" → *armor*; *helmet*; *shell*. From the bronzeware inscription style onward, however, the character becomes a depiction of a hard, seed-bearing *husk*. *First in a series* and *first calendar sign* are borrowed meanings.

[Full Kanji Etymology List]