Arsha prayoga (

Sanskrit Sanskrit (; attributively , ; nominally , , ) is a classical language belonging to the Indo-Aryan branch of the Indo-European languages. It arose in South Asia after its predecessor languages had diffused there from the northwest in the late ...

: आर्षः प्रयोगः) is a common term for such linguistic usages in

, which although not correct as per grammatical rules, are still exempted and deemed valid on account of their having been used by some ancient sages ( rishis).
Literally, word Arsha has following derivation: ::ऋषेरिदम् (अण्) (= That of rishi (usage of ''Aṇ'' suffix)). Its meaning as per Apte's Dictionary is: ::Used by a rishi only, relating to or belonging to sages, archaic, Vedic (opp. लौकिक or classical) As per another legend, it is one of the eight forms of marriage where the bride's father receives a pair of kine from the groom.{{cite book, title=India through the ages, url=https://archive.org/details/indiathroughages00mada, last=Gopal, first=Madan, year= 1990, page
70
editor=K.S. Gautam, publisher=Publication Division, Ministry of Information and Broadcasting, Government of India

Reasons behind deviation from classical grammar

There are several reasons why deviations from Classical Sanskrit grammar exist in some ancient works. One reason is, some works were composed in Sanskrit even before Panini's famous work Ashtadhyayi, and so did not and could not bear conformance with this (later) most influential grammar work. Though there were several schools of Grammar before Panini also, of which Panini gives reference in his work.

Cultural Significance

In practical terms, the word "''Arsha Prayoga''" has acquired both formal(approving) as well as humorous(disapproving) senses. In approving sense, it is used to show that the meaning of the word is so important that the speaker's (or writer's) grammatical mistake (or conscious deviation from grammar) does not matter. While in disapproving sense, it is used in Sanskrit and Hindi, in a humorous way, to point out grammatical ignorance of the speaker (or writer).

References

Sanskrit words and phrases Vyakarana