I am programmer and want to say "The programming language I have never used before" in very short word like "... programming language" What could that be?
There are a few alternatives involving prepositions:
As mentioned, unfamiliar can also be used directly as an adjective applying to the programming language. The "to me" is then implicit in the meaning.
You could try
If you wished to indicate that you were not experienced, but dedicated to learning the language, you might say
[Note: Before I am inundated by the Slash Police, I am not advocating the use of "/" in actual sentences, but merely suggesting a choice.]