This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
顊 combines 阜 (mound, hill) and 頁 (head, page). The exact historical development is uncertain, but it likely originally referred to a part of the head or face, possibly the chin or jaw, given the reading おとがい (chin).
The left side 阜 looks like a mound or hill, and the right side 頁 is a head. Imagine a head with a prominent chin shaped like a small hill, hinting at the reading おとがい (chin).
For イ, picture an eagle (イーグル) perched on a chin-shaped hill: eagle -> イ, and the hill is the chin on the head.