被子
bèi zi · HSK 3
quilt
🛌 被 = bedding cover + 子 noun-suffix; a quilt
被 (bèi) on its own means to cover or a cover/quilt; 子 is a common noun suffix turning it into the everyday word 被子. Measure word is 床 (chuáng), the same word as bed.
被 — clothes radical 衤 + 皮 (skin/hide)
Originally a semantic-phonetic compound: 衤 (clothing) gives the meaning 'blanket/quilt', while 皮 supplies the sound. From 'covering' it extended to 'cover oneself with', then grammaticalized into the passive marker 'by', its most common modern use.
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.