ハチ, や, や.つ, やっ.つ, よう, な, は, はっ, はつ, やち, やつ, はちがしら
eight, eight radical (no. 12)
JLPT5 G1 S2 F92
Two curved lines bending away from each other, suggesting the idea of splitting away to right and left → *divide/part from* right and left. *Eight* is either a borrowed meaning or may be regarded as having been considered the single-digit number divisible by two the greatest number of times.
[Full Kanji Etymology List]