Here's the story:
Each village/port had its own pattern - usually a combination of bars, seeds and cables. The story goes that this meant that if a fisherman was washed overboard his body could be identified by the pattern on the sweater - wool, after all, would survive longer in the water than human flesh!! If there was more than one man in each family the knitters would often add the wearer's initials in the underarm gussets. There is one story of a knitter identifying her son's stolen sweater by asking the new wearer to raise his arms and asking if his initials were, coincidentally, the same as her son's!!