Arsha_prayoga
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, the word Arsha has the following derivation:
Its meaning as per Apte's Dictionary is: