Silk radical on the left — the simplified form of 糸. The original sense of 纳 was 'soaking silk fibres into water before weaving,' which broadened to 'take in, accept, absorb.' Same thread family as 纸, 织, 纺, 线 — anything spun, dyed, or sewn.
Right side 内 carries the sound: nèi → nà with vowel shift, and doubles as a strong semantic hint — 'inner' supports the meaning 'take in, draw inward.' This phonetic+semantic overlap is why 纳 reliably means 'to admit, accept, pay in' (接纳, 缴纳).
