>And then the Milliner — and the Man  
Of the Appalling Trade —  
To take the measure of the House —  
There'll be that Dark Parade —  

**Meaning**:
What you might not know—but Dickinson probably did—is that *"appalling" comes from the Latin word for "**to make pale**,"* as the undertaker was responsible for preparing the body right there in the home.

Could anyone please show me what is the concept or meaning of the italic part?

([Source][1])
  [1]: http://www.shmoop.com/theres-been-a-death-in-the-opposite-house/stanzas-5-6-summary.html