Where does the phrase spitting image come from

[mole221]

what is the origin of spitting image

[novalis]

Brewer's Dictionary of Phrase & Fable gives the following:-
Spitting image or spit the image. An exact likeness or resemblence, just as if one person were to spit out of another's mouth.

[Quizmonster]

If you click here, a link will take you to a web-site run by a noted etymologist which explains.

[heathfield]

I've always considered the 'spirit' explanation to be the most plausible answer to the question, despite Professor Horn's skepticism.

[Quizmonster]

The spitten picter - meaning a strong likeness - was recorded in Cumbrian dialect in the 1870s and the earliest recorded use of 'the spitting image' dates back only to the early 20th century.
Given that picture (picter) and image are effectively synonyms and that two recognised language experts such as Quinion and Horn lean away from any spirit connection, I'd be tempted to lean away from it, too.
On a quick glance, the OED does not seem to have any record of 'spirit and image' as a phrase. However, given that there is some doubt, each to his own!