E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The place under inspection, from the Latin verb tueor, to behold, to look at. It was the space marked out by the Roman augurs as the field of observation. When augurs made their observations they marked out a space within which the sign was to occur. Rather remarkable is it that the Greek theos and Latin deus are nouns from the verbs theaomai and tueor, meaning the presence in this space marked out by the augurs.