The connection is the word "sark". The story of Cutty Sark as popularised by Robert Burns introduces us to the words "cutty sark" which is Scottish for "short shirt". The same sark word appears in the origin of berserk from "bera serkr" a "bear shirt" i.e. a shirt made of furry bear pelt.
However an alternative (and possibly spurious) etymology recounted to me by a mycologist was that berserk had its origins in bare [sic] shirt. His theory was that the Norse warriors were so hopped up on Fly Agaric (Amanita muscaria) that they went into battle bare-chested. And that is how I used to cycle.
In order to arrive at work cool and un-sweaty I would cycle bare-chested the 9.25 miles from South Wimbledon to Devonshire Square, using the wind chill factor to lose the excess heat being generated.
I used to listen to the weather on the radio and if is was above 11°C (52°F) I would cycle bare-chested. If it was below, I would don a T-shirt to keep me comfortable until I warmed up. That was usually the first mile; I would stop at Colliers Wood, strip off and continue my merry way - berserk.
Self inflicted pain, lots of it
5 weeks ago