Old French vs French language

Old French and French language both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old French	Yes	No	No	No
French language	Yes	No	No	No

As nouns, French language is a hypernym of Old French; that is, French language is a word with a broader meaning than Old French:

Old French: the earliest form of the French language; 9th to 15th century
French language: the Romance language spoken in France and in countries colonized by France

Other hypernyms of Old French include French.

Old French (noun)	French language (noun)
the earliest form of the French language; 9th to 15th century	the Romance language spoken in France and in countries colonized by France