"where's that to?"

Question

In Plymouth, and other areas of Devon, it is common to suffix the question "where's that?" with to.

e.g.

Steve: I'm off to see Rita.

Dave: Oh yeah? Where's Rita to?

or

Steve: I'm off to Roborough

Dave: Where's that to?

Is there an origins story for this construction?

Answer 1

The OED, s.v. "to", meaning A.4.a, says

a. Expressing simple position: At, in (a place, also fig. a condition, etc.). Cf. German zu Berlin, zu hause. Now only dial. and U.S. colloq. Cf. home n.1 and adj. Phrases 1e.

It gives examples from 925 to 1977, including this from 1899:

In Somerset‥it is correct to say ‘I bought this to Taunton’.