校 - How did "leg-brace" come to mean "school"?

Question

When learning Chinese characters using radicals, this character 校 always seem to puzzle me. I've always known 校 to be school, but the "wood" 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 "school"?

Answer 1

Outlier

xiào
○ school

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

character that is "borrowed" 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.

Answer 2

Please note "学校" is not a Chinese concept at all

this info is incorrect

“學校” as a term, referred to “school”, is quite ancient. even a simple search in ctext.org have 24 occurrences in literatures before 秦 dynasty:

https://ctext.org/pre-qin-and-han/zh?searchu=學校

most of them means “school”, such as:

獨斷 卷上

三代學校之別名：夏曰校，殷曰序，周曰庠

後漢書 列傳 班彪列傳下

是以四海之內，學校如林，庠序盈門，獻酬交錯，俎豆莘莘，下舞上歌，蹈德詠仁。

後漢書 列傳 鄭孔荀列傳

更置城邑，立學校，表顯儒術，薦舉賢良鄭玄、彭璆、邴原等。

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

unless you have very strong arguments, stick to what 說文解字 said.

校 木囚也。从木，交聲。

it stated clearly that “交” is the phonetic component. making semantic inference from a phonetic component is, imo, improper.

an analog: in the word “starboard”, “star” provided the sound only. if one argued that “starboard” means “a star shaped board”, because the first four characters means “star”, isn’t it ridiculous?

back to “校”, look at the homophone “效”, this character is older.

http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/search.php?word=效

have fun :)

Answer 3

Simplest Answer by Noriko K. Williams 2018.

Now we are ready to look at the kanji 校. By adding 木 “wood” it created a totally different meaning — a pair of shackles over a prisoner’s ankles or neck. Crossing also gave the meaning “to check; compare.” A school is where knowledge gets exchanged between teachers and students, so 校 also meant “school.” Piling logs in an interlocking manner makes a wall, and a house. A military installation had a crossed-log wall or fence, and from that 校 was also used to mean “military officer.”

Short, but abstruse scan of Axel Schuessler's ABC Etymological Dictionary of Old Chinese (2007), page 536.

Longest Answer. I don't have enough reputation to copy and paste the section under

3. Etymology

Answer 4

校 was pronounced jiao instead of xiao in the beginning. It was a military term covering quite wide meaning: to inspect the troops; to practice drill; to compete military skills. The place to do so is always a big open field surrounded by high wood fence, hence radical of wood and the place is 校场。 Please note "学校" is not a Chinese concept at all ("学堂“ was used then as all classes are conducted indoor). It was introduced to China in late 19th century by westerners. The biggest difference is there is always a big field for the students to do various activities, and it looks exactly like 校场 with similar functions。 Not suitable to call it 学堂 anymore, so, call it "学校" emphasizing it's for education, not military. I am not sure, but I think the shifting of pronunciation happened around that time also.