Refers to the pointed tip of an arrow. A straightforward noun with no special usage restrictions.
矢の根が的に深く刺さった。
The arrowhead stuck deep into the target.
Compound of 矢 (ya, 'arrow') + の (no, possessive particle) + 根 (ne, 'root; base'), literally 'the root of an arrow'. The exact historical derivation is uncertain, but the spelling is conventionally associated with the arrowhead.