"expel saliva," O.E.
spittan (Anglian),
spætan (W.Saxon), from PIE
*sp(y)eu-, of imitative origin (see
spew). Not the usual O.E. word for this;
spætlan (see
spittle) and
spiwan (see
spew) are more common. Meaning "to eject saliva (at someone or something) as a gesture of contempt" is in O.E. The noun is attested from c.1300. Meaning "the very likeness" is attested from 1602 (e.g.
spitting image, attested from 1901); cf. Fr.
craché in same sense. Military phrase
spit and polish first recorded 1895.
Spitball is from 1846 in the schoolboy sense, 1905 in the baseball sense.