Phonosemantic compound. 尸 represents the meaning and 𧝑 represents the sound. Based on the original meaning "roll over". The meaning later shifted to "unfold", "spread out", and "develop".
Shuowen Jiezi
《說文》：“展，轉也。从尸，省聲。”
Original meaning
roll over
Components
尸(meaning) — Depicts a person sitting or squatting.