That Dick is short for Richard everyone knows, but why? Very few can explain.
Richard is derived from the Germanic “Rikharthu”– with “Rik” meaning leader and “Harthu” meaning hard. Now, one may think ‘oh right, with a name like that, this arrogant prick must be a dick’. Well not at all. According to Today I Found Out, the reason behind the unfortunate nickname is much simpler. People apparently enjoyed using rhyming nicknames. Richards were called Rick, which rhymes with dick and the rest is history.
On a similar note, “dick” means fat in German. Now you know.