Though spelled and contracted in different ways, spit and image, spitting image, spittin’ image, spitten image, the intent is always the same, an exact likeness, a counterpart.
It usually refers to an infant or child whose features and mannerisms strongly reflect those of one of its parents.
The origin of the expression has been variously ascribed; thus, for example, the late O. O. McIntyre, newspaper columnist, offered the ingenious suggestion that it may have been an American Negro corruption of “spirit and image,” that the child possessed the spirit and was the image of its parent.
In my opinion, however, the expression is partly English and partly American. The records show that “spit,” in such form as “the spit of his father,” was used in England early in the nineteenth century.
It seems certain that the origin of the noun in this sense was derived from an earlier use of the verb, going back over some two hundred years, for earlier records show such expressions as, “as like (a person or animal) as if spit out of his mouth.”
“Image” seems to have been a redundancy added in America. It was not needed, and only serves to intensify the close resemblance which the speaker observes.
Records do not show that the doubled term was in use much before the middle of the past century.