To sock someone means to hit them. This is the case in Ireland, in England or in the States. Nobody knows where this expression comes from. It first appears in English around 1700.
Daniel Cassidy, author of the atrocious How The Irish Invented Slang, tries to match this to an available word in Irish. His chosen candidate is the word sac or sacadh, which is a verb derived from French sac, either directly or through English sack. It means to thrust something into a bag, to shove something, to stick something into or through something. It doesn’t mean to hit someone or something hard, or indeed to hit them at all, so I can’t really see why it would be a candidate for the origin of sock.
Cassidy’s account of the uses of the word sock in English contains one very funny line and as usual in this book, it is completely unintentional.
“To sock someone, means to give them a sac (poke) in the nose.”
This word sac, of course, is poke as in obsolete word for sack or bag (or ice-cream cone in Scotland and Ireland), not poke as in prod or hit someone. Readers of this blog may have noticed that I am not a big Daniel Cassidy fan but sometimes even I am stunned at the level of this man’s stupidity, ignorance and laziness.