ハク, ビャク, しろ, しら, しろ.い, あき, か, はっ
JLPT5 G1 S5 F483
A depiction of an acorn, a large number of which would be scattered over the ground. The meaning *white* is by association with the color of acorn meat. For "large number," compare 百.
[Full Kanji Etymology List]