Arsha prayoga (Sanskrit: आर्षः प्रयोगः) is a common term for such linguistic usages in Sanskrit, 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:
Contents
Its meaning as per Apte's Dictionary is:
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).