E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Half-seas Over.
Almost up with one. Now applied to a person almost dead drunk. The phrase seems to be a corruption of the Dutch op-zee zober, over-sea beer, a strong, heady beverage introduced into Holland from England (Gifford). Up-zee Freese is Friezeland beer. The Dutch, half seeunsts over, more than half-sick. (C. K. Steerman.)