Khas Kura used to be the language of Khas Empire of Western Nepal (11th-14th century). Khas language was already a developed language by then. Gorkha was one of the successor kingdom of Khas Empire after it broke down. As Gorkha united all small kingdoms in the himalayan region during 1744-1791, Khas language then called Gorkhali language. When that country started to referred as Nepal as a whole, Gorkha language became Nepali language.
The oldest available written text of Nepali language is Bhupal Damu Pal’s stone-manuscript at (Sak Sambat 903 - BS 1038 - AD 981). The language used is near to Dotel-dialect.
The text of the stone manuscript is as follows:
ॐ ………पद्मे हुं । ……… दामुपाल भूपाल रेख भई । किष्णु अडैको भाइ सउँपाल अडै सा(के) ९०३ ।
// OM Padhem Hun..Damupal Bhupal Rekh bhai. Kishnu adaiko bhai saupal adai sa(ke) 903.
English: Pray to Padmanav Buddha. … The border of land (donated will be ) as borderred by King Damupal. To Adaya (Officer?) Som Pal, brother of Adaya Krishnu. > Probably King was donating some land to one of the officer (Som Pal) who was brother of another main officer (Krishna- localised as Krishnu). The border of land was fixed by the King in this manuscript.
King Nagraaj (1093 AD) is known as the first King of Khas empire. We find many stone manuscript during Khas era (11th-14th century) written in Khas/Nepali language.
But Nepali language has evolved a lot since then. Though core of Nepali language directly inherit Sanskrit language components, the current Nepali language borrows a lot of words from Tibeto-Burman languages of the Himalayan region like Limbu, Gurung, Magar, Rai, Bhutia, Lepcha, Tamang, Sherpa and also from other Indo-Europian langauges like English, French, Hindi, Urdu, Persian etc and from other languages like Arabic.
Literature
Nepali literature has existed in verbal folklore for the past hundreds of years; however, as early scholars wrote in Sanskrit, Nepali literature in written form is relatively new.
Shuwananda Das (2 of Shadhya ko kabi), Radha Ballav Arjyal (1 Shadhya ko kabit), Shakti Ballav Arjyal ("Hanshyakaduba" to Nepali translation from his own sanskrit work), Udaya Nanda Arjyal, Bhanu Datta( translated "hitopadesh mitralav" in 1833), Pt. Divya Kasheri Arjjyal (1847-1904: Goraksha Yog shastra), Gumani Pant (1847-1904), Bir Shali Panta (Bimalbodhanuvaba), Bidhya Kasheri Arjyal(1863-1912 : Ugal Geet,Droupadi Stuti) etc were early Nepali poets who primarily wrote in Sanskrit but also in Nepali language. Writers of that era wrote upon the war and bravery.(Link)
Hindu epic Ramayana was translated from Sanskrit to Nepali by Bhanubhakta (1814-1868) who is now known as Aadikavi, the first poet of Nepali language. Manuscript of Bhanubhakta was first published in 1887 by another poet Motiram Bhatta (1866-1896), who himself pioneered Ghazal, a poetic form of literature, in Nepali language.
Music/ Song
Tradition of Music is way older in Nepal then Nepali language. Classical Music was already in existence at the time of first recorded history of Nepal (King Mandev 510AD).
Existence of Nepali language in melodious spoken form is as old as Nepali language itself. Tradition of Dohori (a duet form of music) and Rodi-Ghar (nightly gathering place for youth for musical entertainment) has been prevalent in different ethnic groups of Nepali society since long. Siloke is another literature/musical tradition in Nepal. Silo-ke was the person who used to recite / sing Silok (melodical verse) in front of people during wedding ceremony. So where ever Nepali language was spoken, its obvious to see those tradition followed in that language.
Seturam Shrestha (1891-1941) is believed to be the first recording artist in Nepali language. He recorded his song in 1908 on gramophone disc.
Movies/Theatre
Satya Harischandra became the first movie made in Nepali language in 1951.
References:-
Panch Saya Barsa edited by Prof. Balkrishna Pokharel.
Stone Manuscript of AD 981 was collected by Purna Prakash Yatri.
See Also