Source: In common use
Inome (猪目) literally means "boar's eye". They are heart-shaped elements that often feature on Japanese arms and armor, including tsuba and other sword mounts, arrowheads, polearm mounts, etc.
The inome refers to the bravery and determination with which a provoked wild boar would attack his attacker.
A Japanese arrowhead, yanone, with boar's eye cutout.
Metropolitan Museum accession number 32.75.357.
From the Collection of Giovanni P. Morosini, presented by his daughter Giulia, 1932.
A sword guard with four inome cutouts on each corner. A typical shape for tachi guards.
1. Markus Sesko; Encyclopedia of Japanese Swords. Markus Sesko Print and Publishing: Lulu Enterprises, 2014. Page 135.