甲
jiǎ · HSK 5
first of the ten Heavenly Stems
🥇 甲 = 'first' Heavenly Stem; also means shell/armor (turtle shell shape origin)
Etymology: oracle-bone 甲 depicted a cracked turtle shell or seed sprout shell, hence 'shell/armor'. Reused as the FIRST of the 10 Heavenly Stems (天干), so 甲 = #1, like 'Plan A' or grade-A.
甲 — pictograph of a seed sprout's hard shell
甲 originally pictured the cracked shell of a seed as it sprouts, or the hard carapace/armor of a turtle or insect. From this came meanings like 'shell,' 'armor,' and 'helmet.' It was later borrowed as the first of the ten Heavenly Stems, giving it the sense of 'first' or 'A-grade.'