These terms were devised in the late 20th century analysis of Classical Japanese, originally, for the difference between -(さ)す (glossed as externally instigated) and -(ら)る (glossed as internally instigated). This exoactive vs endoactive reflects 18th century Japanese use of 他動詞 vs 自動詞 (tadoushi vs jidoushi).
In more traditional Western-orientated linguistic ...
On p. 43 of ABC Etymological Dictionary of Old Chinese By Axel Schuessler we have the following introduction:
which is later expound on:
On p. 44 we find the exact example that you are asking about:
It also comes with an explanation:
There is a little explanation also here:
[...] endoactive (introvert) verbs also can be tr. like mai 'to buy (something)',...
in ancient china, the right angle triangle is named "勾股形".
the 國語辭典 has this entry: 勾股, explained as
the short side near the right angle is called "勾", the longer side near the right angle is called "股"; and the side opposite the right angle is called "弦".
people used something like "勾股", "勾股之法" to ...