素
ソ, ス, もと
elementary, principle, naked, uncovered
JLPT1 G5 S10 F660
糸# thread + an abbreviated form of 垂 hang → pendent white/raw silk → *element*; *basis*; *simplicity*; *from the beginning* (← raw silk forming the basis of fabric and clothing woven from it).
[Full Kanji Etymology List]