ショウ, さかん, まさ, まさし, よし, あき, あきら, さかえ, あつ, すけ

prosperous, bright, clear

JLPT1 G13 S0 F1372

Originally, an abbreviated form# of (bright) + say/speech indicator → chant/recite in a *bright*/*clear* voice → *prosper* (← bright conditions). A seal inscription form simplifies the character to + sun/day.

[Full Kanji Etymology List]