Indo-European vs Indo-Germanic

Indo-European is a noun but Indo-Germanic is not a noun.

Word	Noun	Adjective	Verb	Adverb
Indo-European	Yes	Yes	No	No
Indo-Germanic	No	Yes	No	No

As adjectives, Indo-European and Indo-Germanic are synonyms defined as:

Indo-European and Indo-Germanic: of or relating to the Indo-European language family

Indo-European (noun)	Indo-Germanic (noun)
the family of languages that by 1000 BC were spoken throughout Europe and in parts of southwestern and southern Asia
a member of the prehistoric people who spoke Proto-Indo European

Indo-European (adjective)	Indo-Germanic (adjective)
of or relating to the former Indo-European people	of or relating to the Indo-European language family
of or relating to the Indo-European language family