E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Thats Exter, as the old woman said when she saw Kerton. This is a Devonshire saying, meaning, I thought my work was done, but I find much still remains before it is completed. Exter is the popular pronunciation of Exeter, and Kerton is Credition. The tradition is that the woman in question was going for the first time to Exeter, and seeing the grand old church of Kerton (Crediton), supposed it to be Exeter Cathedral. Thats Exter, she said, and my journey is over; but alas! she had still eight miles to walk before she reached her destination.