title: What does CSS measurement unit 'em' actually stand for?
body: <p>As the title says, I want to know what exactly the CSS unit 'em' stands for.<br>
  As in 'cm' stands for <b>c</b>enti<b>m</b>eter.</p>
  
  <p>I am not asking what 'em' is or how it is used!</p>
  
  <p>I couldn't find an answer on <a href="http://www.w3.org" rel="noreferrer">W3C</a>.<br>
  The <a href="http://en.wikipedia.org/wiki/Em_%28typography%29" rel="noreferrer">Wikipedia</a> article was already saying "something":</p>
  
  <blockquote>
    <p>The name of em is related to M. Originally the unit was derived from the width of the capital "M" in the given typeface.</p>
  </blockquote>
  
  <p>My interpretation of the first sentence would be that 'em' is the pronunciation/phonetic for the letter 'M'.<br>
  But reading the second sentence, it seems that the 'e' in 'em' stands for something regarding the width of the letter 'M'.<br>
  So I'm still lost, what 'em' really stands for!</p>