Mike, In answer to your original question: I'm sure the two names, Smith and Smithie , became confused in use and in transcribing. On many registers the clerk would ask the personsssss involved their nam,e and write it down as he heard it. Quite often the person giving the name would not be literate- or would not have the opportunity to check what had been written.
This is that case in a great many surnames,e specially when the spoken name can be written in various ways that approximate to the stated name.
If everything else fits, my attitude is to investigate the match further and try to check against other data. Slow but a reasonable way to proceed.
charlotte
