[Advaita-l] अनिर्वचनीया ख्याति anirvacaniiyaa khyaati post-Shankara origin?

[Raghav Kumar Dwivedula]

Namaste
In Advaita vedanta, the model to explain erroneous perceptions (such as
seeing a snake instead of the actual rope) is that  of अनिर्वचनीया
ख्यातिवाद (anirvacaniiyaa khyaati-vaada). This is used to explain that
erroneous perceptions are neither categorically real nor categorically
unreal.

"If its real, then it would never get negated/sublated; if it is unreal
then it would never be experienced at all.(सच्चेत् न बाध्येत ; असत् चेत् न
प्रतीयेत)". Therefore the erroneous perception is labelled anirvacaniiyaa
khyaati. This is the idea.

Is this idea of anirvacaniiyaa khyaati presented in Shankara Bhashya? Or
was it of later origin? Also, do some advaitins hold that this
anirvacaniiyaa khyaati-vaada was of later post-Shankara origin?

Thank you in advance for any light on this matter.

Om

Raghav