Depicts a person with an emphasized eye (𦰋) sleeping on a bed (爿), conveying the meaning "dream". 𦰋 also represents the sound. The 爿 (bed) component was later reanalyzed as meaning component 夕 (evening).
Shuowen Jiezi
《說文》：“夢，不明也。从夕，瞢省聲。”
Components
𦰋(sound, iconic) — Depicts a person (人) with an emphasized eye (𥄕).
夕(meaning) — Originally 爿, which depicted a bed. Later reanalyzed as meaning component 夕 (evening).