Now if you were a transcriber, what would you record for DO DO on a list...

[majm]

It is actually on a typed document....

London, England, Electoral Registers, 1832-1965 

Likely there's an OCR machine involved ... well that's my excuse for the foolishness.

Name:   Do Do
Year:   1945
County or Borough:   Finchley
Ward or Division/Constituency:   Friern Barnet

        HUNDREDS of Do Do resided there in 1945, their names are clearly displayed, 

Ancestry has much to answer for
Ditto        "     do     etc  etc   etc

ADD
and for  DITTO .... just as bad...

Name:   Nurses Ditto
Year:   1932
County or Borough:   Greenwich
Ward or Division/Constituency:   Greenwich

JM

[Mart 'n' Al]

Stories like this make me consider changing my name to Martin Ditto.

Martin

[majm]

JM Ditto here

[Mart 'n' Al]

JM, are we related then?

Martin

[majm]

No, No, No,   

[Mart 'n' Al]

So you are saying that poo from an extinct bird is Dodo do do? And if I repeat myself it's dodo do do ditto?

Martin

[majm]

yes yes yes

[majm]

but its all in the context

[JohninSussex]

Without seeing what the original looks like, this seems to be a serious issue.
An electoral register should not have "Do" in the name column, it's not like the census schedules.  But it would be quite natural in the address column, because especially in urban areas electoral registers are arranged by street so the entries might look like

Jones Robert, 1 Roots Street
Do Cynthia, 1 Do Do
Smith Bertram, 3 Do Do
Do Barbara, 3 Do Do
Martin George, 5 Do Do
...

and assuming the computer can cope with the Do surnames (which actually I have never seen) somehow it is presenting the address as if it was the name.

So does that database show an abnormally large number with the surname Street, Avenue etc?