Rookie Rock Fan Mistake
Overheard: “Eric Clapton was called slowhand because he played the guitar quite slowly.”
Clarification:
The Yardbirds rhythm guitarist, Chris Dreja, recalled that whenever Eric Clapton broke a guitar string during a concert, Eric would stay on stage and replace it. The English audiences would wait out the delay by doing a “slow handclap”. [The British colloquialism is “to be given the slowhand”.
More here: http://www.whereseric.com/eric-clapton-faq/biographical-information-eric-clapton/how-did-eric-clapton-get-his-nickname-slowhan