forevouch means to avow or affirm in advance. Lexicurio rates it Sui generis — a strength score of 93 out of 100.
Etymology
From fore- + vouch.
verb
- To avow or affirm in advance.“And His own psalm in Hades had been forevouched for centuries, predicting His release from the grave and the intermediate world, and his reentrance into life, and assuming "the path of (unending) life."”