What would D.O.R.A. have meant in 1929?

I recently started reading a strange little book from 1929 called Breaking Priscian’s Head, or English as She Will Be Spoke And Wrote, by a Scotsman named J. Y. T Greig. In a passage about how some words drop out of the language because the things they describe are no longer in use, Greig mentions the words "hansom", "four-wheeler", and "D.O.R.A.", expressing considerable happiness at the disappearance of that last one.

So, it turns out that Greig was absolutely correct about the disappearance of "D.O.R.A", and I haven’t the faintest clue what it could possibly mean. A quick Google search yields nothing that seems applicable to the 1920s. Do any of you have any ideas?

Here’s a picture of that page, by the way: