E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Like an owl in an ivy-bush. Having a sapient, vacant look, as some persons have when in their cups; having a stupid vacant stare. Owls are proverbial for their judge-like solemnity, and ivy is the favourite plant of Bacchus. Gray, in his Elegy, refers to the Owl and the Ivy.