Where does “Middle-earthian” come from?

Middle-earthian (English) comes from English Middle-earth, from English Middle Earth, from Middle English myddelerthe, from Middle English myddelerd, from Middle English myddenerd, from Old English middaneard, from Old English middanġeard, from Proto-Germanic midjagardaz — in the middle of, near, by, around, with.

Middle-earthian (English): Of, resembling, or characteristic of, Middle-earth

Definitions

Of, resembling, or characteristic of, Middle-earth

Ancestry of “Middle-earthian”, step by step

Middle-earthian traces back through two separate lines of ancestry.

via English Middle-earth

Step	Language	Word	Meaning
1	English	Middle-earth	The main setting of J. R. R. Tolkien's Lord of the Rings and other works
2	English	Middle Earth	The Earth
3	Middle English	myddelerthe	The Earth; the world as between Heaven and Hell or in the middle of the universe
4	Middle English	myddelerd	The Earth; the world as between Heaven and Hell or in the middle of the universe
5	Middle English	myddenerd	The Earth; the world as between Heaven and Hell or in the middle of the universe
6	Old English	middaneard	—
7	Old English	middanġeard	the world
8	Proto-Germanic	midjagardaz	middle-earth; middle enclosure
9	Proto-Germanic	midjaz	middle, mid
10	Proto-Indo-European	médʰyos	middle
11	Proto-Indo-European	medʰi-	with, among; with, along
12	Proto-Indo-European	me	in the middle of, near, by, around, with

via English ian

Step	Language	Word	Meaning
1	English	ian	—
2	Irish	Eoin	John any of several people in the Bible
3	Old Irish	Iohain	John apostle
4	Latin	Iōannēs	John biblical persons
5	Ancient Greek	Ἰωάννης	—
6	Hebrew	יוחנן	Yahweh is gracious
7	Hebrew	חנון	gracious, merciful, compassionate; passive...
8	Moroccan Arabic	خنونة	mucus, snot
9	Arabic	خُنَّة	—

Every word from Proto-Indo-European me →Every word from Proto-Indo-European medʰi- →Every word from Proto-Indo-European médʰyos →