tika bro, let me take u back to the history, this nepali language which we generally speak is as u said developed by khas jati, and it is particularly their language.... but, the main point is, at those days may be u had ur language i.e. tharu or hindi whatever, and other people had their own languages according to their community and religion. but why didn't other languages developed and spoken as national language ?? its simply because, the majority of people in nepal spoke nepali language at that time and other people followed it, there was no any force for them to use nepali language, but instead of supporting their own language they started speaking in nepali language.. that means larger community gets more priority, its not because of people in power forced others to use nepali language...

and as u mentioned parbate language was later called gurkha language during gurkhs rule, but do u still know the fact that the language spoken in gurkha was different then nepali ??? gurkha is typically gurung society and they spoke gurung language at that time, so u better don't link nepali.... if u still know the fact of nepal then there are more than 40 types of rai in nepal and all of them have their separate languge according to the cast and community..

now let me tell u how nepali language was developed........ at the time of gautam buddha, pali language was famously used all over asia, so, u find lots of scripts written in pali from those period.... there were small kingdom and community in nepal who had their own language, but to communicate with each other (communities), they used pali language and later on as per the ascent and native language different improvised versions of pali came to existance.... and the saha dynasty who came from far farsi land improvised the same pali language mixing some words and pronounciation from farsi language.... after nepal was unified the language was given the name called nepali, which is improvised version of pali.... there are still lots of improvised version of pali language in the world, and they improvised that language according to their community.... u can hear tibetan, jonkha, etc, they are improvised from pali.

As u were stucked in khas jatis, yes they were the most educated persons in nepal, majority according to the population too, but still khas jatis in east nepal and khas jati in west nepal they had different languages, if u didn't know.... and till now, deuda language is most famous in western nepal.... and let me tell u about khas jatis... they were educated and they used to go india, specially banaras to study sanskrit.... and before hindu territory uttar prades was famous place among muslims from west, who migrated there... their language was urdu and now what language u usually use hindi is also an improvised from urdu language.... the people from banaras started a script called devanagari, which was derived from sanskrit scripts, and those nepali people studying there used that script as form of written language... after coming back to nepal, they started writing each and every thing in that script and mixed pali + sanskrit words.... they taught most of other peoples to read those scripts, which eventually became famous..... every people who learned that script started writing about their feellings and many other things, etc etc.. this how people started learning things, and in modern era, people started writing stories, peoms, essays, letters using devanagari script in nepali language.... if u still read those articles written at earlier stage of devanagari script, then u may not understand it, cause it was different improvised version of pali + sanskrit language, because they contain lots of pali and sanskrit words... but in later stage the writings were given a new form by formation of grammar, vowels and verbs which instructed writers to follow some rules and criterias, and so new nepali language was created... with perfect grammar and word formation.... and there were several articles written in nepali language that all other communities have to follow it, not by force, because nepali language was famous and was subject of interest for them, because of great peoms and stories, etc, etc...

I know what is in ur mind now, u might be thinking nepali language was improvised from sanskrit, yes u r right my friend, pali language is improvised from sanskrit and nepali was improvised from pali + sanskrit.....

and let me tell u one more fact, at that era nepali language was used specially in eastern language and till now u can see most of the nepali articles are written by mid and eastern nepali people, and people from west nepal were bound to follow the language because of the popularity of language at that time, some of them followed indian language and they have deuda language, which contains lots of hindi words, but still it sounds different then hindi or nepali.... and maximum of people followed nepali language and devanagari script because most of the articles written by nepali people was in nepali language and devanagari script, so, it was compulsory taught in schools.. and laxmi parsad devkota was our education minister at that period who made this rule and strictly instructed all the schools in nepal to teach this language..... may be he made compulsion for people like u to learn this language, but just imagine what will ur condition be if u have not learned to read and write.... angutha chhap.... so, he made this rule to educate the people which was practically successfull....

our nepali language has soooo long history and it have struggled through different periods and finally formed  a good means of communication between nepali people, now, u r saying it is just khas language.... where the f.u.c.k. ur tharu language and other languages were at those periods of struggle?? if ur community had such big concern at that time then they would have come with different language and different script to write, and how many articles, peoms, essays or stories u have read in ur language??? I guess it can be counted in finger.... so, at this period, after all the structure is formed u cannot say nepali language is just khas language, it is and was used by even ur community and all other peoples in nepal..... now u have come up with ur new idea of hindi language to communicate with nepali people then u r making fool of yourself.... nepali language may have beed generated and developed by khas, but it was practically used by all the communities as a means of communication in nepal.... so, it was named national language of nepal.... there are several other national languages of nepal like newari, maithili, etc. but the majority of people use nepali.... so, please come up with good idea then to murmur what u read in wikipedia.... I know u searched in wikipedia for nepali language which described nepali language as khas parbate and gurkha and later nepali, but wikipedia is not right all the time, it might be updated by peoples like u full of passimistic ego... i know we can't see our a.s.s but we don't have to ask someone if we have hole on our a.s.s.... so, don't dig ur dignity just know ur identity, if u r nepali and u stay inside territory of nepal, and if u can read, write, speak and understand nepali, then better use nepali... be proud of what u r then to hook a pin in ur identity.....