広
コウ, ひろ.い, ひろ.まる, ひろ.める, ひろ.がる, ひろ.げる

wide, broad, spacious

JLPT4 G2 S5 F263

As per 黃# (extend) + 广 building → long building that extends far over its locale → *stretch*; *extensive*; *spacious*; *vast*; *spread*; *widespread*; *enlarge* → *be popular* (← widespread popularity).

[Full Kanji Etymology List]