prewarn means to warn beforehand; to forewarn. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
From pre- + warn.
verb
- To warn beforehand; to forewarn.“The credited testimony of Borden shows that Adams on October 12 prewarned him about the discharge and told him that the ground for the discharge would be the misshading of materials ( i.e. selecting materials for manufacture into a batch of shirts which were not of matching shades).”