|... 'neglected by legends' ... Leanne Moden|
A Univocalism is a piece of writing, emanating from the constrained writing techniques of Oulipo. A Univocalism only allows for the use of one vowel, which may be repeated.
There is a rather good poem, keep my secret, in this style here on the Cambridgeshire NaPoWriMo site by Leanne Moden of Ten Years' Time.
You might also enjoy reading about, or experimenting with, the Lipogram, a 'back formation' with a long history ...
The Lipogram is joined by the Liponym and the Liponol.
You can read about the Transgram here.