The etymology of "pork" is well known, derived from Latin porcus via proto-IndoEuropean porko:
porko: young pig. pork; porcine. porpoise: pigfish. It porcellana; relating to a sow; hence the cowrie: Venus shell, from its resemblance to a sow's vulva; from the hard shell, applied by Marco Polo to Chinese ware, via Fr, came porcelain. Du, aardvark: earth pig, a burrowing animal; muzzled hogs have long been used in Spain to root up truffles. Gc, farrow.
Was porcus brought via porcine by the French swine? Was Old English
a corruption of these? And if so, was picq even the true forebearer of "pig"?
A symbolic form in a language describes (not perhaps very satisfactorily) that class of word that stands somewhere between onomatopoeic words like cuckoo and sizzle on the one hand and ordinary non-echoic words like beauty and bedstead on the other. As one authority puts it, such forms 'have a connotation of somehow illustrating the meaning more immediately than do ordinary speech-forms'. . . .
One symbolic group that has not attracted so much attention is typified by the word pig. 'Rightly is they called pigs,' said some fictional character, presumably a townsman, after a look at life in the sty. So it could be a term of contempt or even loathing, whether applied by an old-fashioned farmer to a domesticated animal or by a slightly less old-fashioned demonstrator to a policeman. That demonstrator might care to know, by the way, that that use of pig was first recorded in the year 1812, only a dozen years after the first policeman or such figure appeared in London. Meaning the animal, pig began to drive out the older word swine in the early nineteenth century, meaning a person probably about 1860.
Pig, it will readily be agreed, is a monosyllable (therefore emphatic) beginning with the sound pi-. There are only a limited number of these possible in English, but three of them do, or can, carry contempt: pimp, the archaic exclamation pish, and good old piss, a term of strong execration when uttered on its own. . . .
Of course, "swine" also has derogatory connotations, we can see their application in the Latin precursor sus in the Vulgata:
which Shipley renders as "Like a gold ring in a swine's snout is a beautiful woman without discretion."
If Amis is right, "pig" appears to have been applied to the police relatively quickly after their appearance, and before solidification of its application to swine. If derived from picgbréad [where is the attestation of picq alone?], then why does its use as a modifier predate its use as a noun? Could contempt for the French oppressors have motivated the derogatory connotations and near immediate application to law enforcement? Or perhaps the nature of the policeman's job is such that comparison with swine is inevitable . . .