How did 賃 get its 慣用音 reading?


賃 has the 慣用音 reading ちん, as in 家賃{やちん}.

I understand that a lot of 慣用音 readings arise from interpreting the phonetic
wrongly (for example 消耗{しょうこう} vs 消耗{しょうもう}), but in this case how did 賃
receive the reading ちん?

I'm having trouble seeing how it could be connected to ちん, when the 呉音 and 漢音
are にん and じん respectively.




[This thesis (note: pdf will
download)](https://seitoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=195&item_no=1&attribute_id=20&file_no=2)
seems to give a taxonomy of 慣用音. And acutally Eiríkr Útlendi's conjecture is
correct (or no other way to justify it). 賃 is categorized as an example of
漢音の清音化 （ぢん → ちん）on p137.

慣用音 means after all 'the way it is pronounced', and how they arise may not be
unique and ultimately unkonwn.

