ニチ, ジツ, ひ, び, か, あ, あき, いる, く, くさ, こう, す, たち, に, にっ, につ, へ
day, sun, Japan, counter for days
JLPT5 G1 S4 F1
A depiction of the *sun* → *day* (← appearance of the sun ushering in a new day). As with 熱, the heat of the sun was understood in terms of softening objects and/or reducing them in size.
[Full Kanji Etymology List]