"spittoon," 1779, a colonial word, from Portuguese cuspidor "spittoon," from cuspir "to spit," from Latin conspuere "spit on," from assimilated form of com-, here perhaps an intensive prefix (see com-), + spuere "to spit" (see spew (v.)).
word-forming element usually meaning "with, together," from Latin com, archaic form of classical Latin cum "together, together with, in combination," from PIE *kom- "beside, near, by, with" (compare Old English ge-, German ge-). The prefix in Latin sometimes was used as an intensive.
Before vowels and aspirates, it is reduced to co-; before -g-, it is assimilated to cog- or con-; before -l-, assimilated to col-; before -r-, assimilated to cor-; before -c-, -d-, -j-, -n-, -q-, -s-, -t-, and -v-, it is assimilated to con-, which was so frequent that it often was used as the normal form.
Old English spiwan "spew, spit," from Proto-Germanic *spiew- (source also of Old Saxon spiwan, Old Norse spyja, Old Frisian spiwa, Middle Dutch spijen, Dutch spuwen, Old High German spiwan, German speien, Gothic spiewan "to spit"), from PIE *sp(y)eu- "to spew, spit," probably ultimately of imitative origin (source also of Latin spuere; Greek ptuein, Doric psyttein; Old Church Slavonic pljuja, Russian plevati; Lithuanian spiauti). Also in Old English as a weak verb, speowan. Related: Spewed; spewing.