glossopoeia
The creation of constructed languages for artistic purposes; language so created.
uncountable
Still more curiously, English offers a second pair of homophones — “hew” and “hew” — with a quite similar range of antonymous meanings, opening the possibility of a glossopoeia of a most cunning and pleasing sort.
Where it comes from
From glosso- (“language”) + -poeia (“making”); coined by J. R. R. Tolkien.
Adapted from the Wiktionary entry glossopoeia (CC BY-SA 4.0).