鋭
エイ, するど.い, とし

pointed, sharpness, edge, weapon, sharp, violent

JLPT2 G7 S15 F1395

As per 兌# (strip away) + 金 metal → strip away flesh with a *sharp* pike → *pick/select* (soldiers) (← pick out only the sharpest fighters) → *zeal*; *enthusiasm*.

[Full Kanji Etymology List]