Methyl hydrate? A methyl group plus water: CH3-<nothing> • H2O? Does not compute, contains free radical. One presumes you mean methanol, CH3-OH, which you could just about call Methyl Hydroxide if you're not scared of the IUPAC naming hit squad. There are lots of alternative and traditional names for methanol but "methyl hydrate" is just plain wrong.
It may not be a "good" name, but the fact remains that it is often sold as methyl hydrate.
I honestly have no idea where the methyl hydrate name came from and you're right, I agree that it really doesn't make any sense, but it's not my fault, I don't make the product labels.
According to Wikipedia, other names for methanol include:
Carbinol, Columbian spirits, Hydroxymethane, MeOH, Methyl alcohol, Methyl hydrate, Methyl hydroxide, Methylic alcohol, Methylol, Pyroligneous spirit, Wood alcohol, Wood naphtha, and Wood spirit.