I thought of the same thing, but it turns out that sense of the word is unrelated.
The traditional shape of the molds used for pig iron ingots is a branching structure formed in sand, with many individual ingots at right angles to a central channel or "runner", resembling a litter of piglets being nursed by a sow. When the metal had cooled and hardened, the smaller ingots (the "pigs") were simply broken from the runner (the "sow"), hence the name "pig iron".
The essay includes several bits of advice for improving security in our field. IMHO, we overlook this one far too often: