校 - How did "leg-brace" come to mean "school"? When learning Chinese characters using radicals, this character 校 always seem to puzzle me. I've always known 校 to be school, but the &quot;wood&quot; radical never made any sense to me. What does wood or tree have to do with school? Why not use a radical that is related to buildings (广 or 宀) or even children (as in 学).
My research on shuowen says that the original meaning was some sort of beam where prisoners' legs were shackled to. This to me makes sense even with the phonetic 交 representing a prisoner shackled to a leg brace with his legs crossed. My question is when, and how did 校 suddenly come to mean &quot;school&quot;?
Outlier

xiào
○ school

Here the ○ icon is an indicator of a phonetic loan. So, basically it is just a:

character that is &quot;borrowed&quot; to write another homophonous or near-homophonous morpheme

It seems that the earliest reading was jiào and not xiào; 校 was just borrowed for its close proximity in sound.