c.1300 (early 13c. in surname Porkuiller), "flesh of a pig as food," from Old French porc "pig, swine, boar," and directly from Latin porcus "pig, tame swine," from PIE *porko- "young swine" (cf. Umbrian purka; Old Church Slavonic prase "young pig;" Lithuanian parsas "pig;" and Old English fearh, Middle Dutch varken, both from Proto-Germanic *farhaz).
Pork barrel in the literal sense is from 1801, American English; meaning "state's financial resources (available for distribution)" is attested from 1907 (in full, national pork barrel); it was noted as an expression of U.S. President President William Howard Taft:
The magazine article that includes the quote opens with:
Pork in this sense is attested from 1862 (cf. figurative use of bacon). Pork chop is attested from 1858. Pork pie is from 1732; pork-pie hat (1855) originally described a woman's style popular c.1855-65, so called for its shape.