咲
ショウ, さ.く, ざき, さ, さき
blossom, bloom
JLPT2 G7 S9 F1534
芺# is as per 夭 (slender and limber) + 艸 grass/plant → slender and limber plant. The addition of 口 mouth suggests a slender opening of the mouth in smiling/laughing. 咲 is a variant of this character. *Blossom* and *bloom* are borrowed meanings, via a literal construing of the expression 鳥鳴花咲 (Birds sing, flowers open).
[Full Kanji Etymology List]