磕
kē , kè · HSK 7
to knock
🚪 石 stone radical + 盍 phonetic: to knock something against a surface hard as stone
The 石 (stone) radical signals hard contact; 盍 carries the kē sound. Shows up in 磕头 (kē tóu), to knock the head on the ground in a kowtow, and in knocking ash from a pipe or mud off boots.
磕 — stone 石 + together 盍 (phonetic)
A phono-semantic compound. The stone radical 石 gives the meaning, pointing to the act of striking something hard like stone, while 盍 supplies the sound. From 'knock against stone' it broadened to mean knocking, bumping, or kowtowing (磕头).