<p>To be honest, I was not even aware of the term "dummy variable trap" until a few days ago, but it seems like <a href="https://stats.stackexchange.com/search?tab=newest&amp;q=%22Dummy%20variable%20trap%22">the term is popping up more and more frequently at CV</a> (note chonological ordering).</p>

<p>Do we need a tag for this? Maybe look for a canonical answer (e.g., <a href="https://stats.stackexchange.com/a/222128/1352">this one</a>, though it goes into many other aspects of collinearity besides the "trap")?</p>
