crooked bones
骪 centers on the idea of bones that are not straight: crooked, bent, or deformed. The given meaning "crooked bones" is the core concept.
骪 combines 骨 (bone) with 凡, which likely contributes a phonetic element. The exact historical development is uncertain, but the character is associated with the idea of crooked or bent bones.
The left side 骨 means bone, and the right side 凡 looks like a bent or twisted shape. Picture a bone that has been warped into a crooked form, like a bent rib.
For イ, imagine an eagle (イーグル) with crooked bones in its wing: the 'イ' sound from eagle cues the reading, and the bent wing matches the meaning.