title: What is key_0, why am I seeing it in my merged dataframe, and is there a way to prevent it?
body: <p>Python 3.6.5 and Pandas 0.23.0 according to my juptyer notebook query.</p>
  
  <p>I'm merging two dataframes:</p>
  
  <pre><code>df_merged1=pd.merge(df_RL, df_BR, how='left',left_on=df_RL['Business Service Manual'], right_on=df_BR['Names'])
  </code></pre>
  
  <p>The left dataframe df_RL.dtypes</p>
  
  <pre><code>Server                     object
  Server Farm                object
  Business Service Manual    object
  dtype: object
  </code></pre>
  
  <p>The right dataframe df_BR.dtypes</p>
  
  <pre><code>Names    object
  dtype: object
  </code></pre>
  
  <p>The resulting merged dataframe df_merged1.dtypes</p>
  
  <pre><code>key_0                      object
  Server                     object
  Server Farm                object
  Business Service Manual    object
  Names                      object
  dtype: object
  </code></pre>
  
  <p>This syntax does what I want it to do for the most part. It's merging my left and right dataframe on 'Business Service Manual' from the left dataframe and 'Names' from the right dataframe.</p>
  
  <p>My issue:
  The resulting merged dataframe adds a column called "key_0" that appears to be the exact same as Business Service Manual.
  What is it? Why is it? Is there a way for me to prevent it from being added in the merge syntax?</p>