I doubt it was a nickname, but I could squint and look sideways and see it as being misspelled. If you shorten Elizabeth to Eliza and compare it to Kezia, they're not that far apart. Don't know how many times I've come across Census data that was either written poorly or transcribed poorly and the result was something close to the name, but not accurate. Plus on some of the Censuses, the taker asked them to speak the names, and then the taker wrote it down how they heard it - and there were occasions where they did not verify before they put it in the books.