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)
It's important to recognize that Latin is not English. The Latin root (such as "to make pale") of an English word ("appalling") will rarely make sense on their own. "To make pale" is ungrammatical as a direct translation to English.
That being said, it's likely that it means that "to make pale" is to make a person go pale, usually at disgust or horror. This fits the scene if I'm correct in saying that it's from when a death occurs.
The Free Dictionary: To cause to turn pale.
I wouldn't take too much notice of the possibility that the author knew the Latin origin of appalling, with reference to making pale (light-coloured).
It doesn't seem particularly relevant to the poetic context here, where most readers would probably be put in mind of pallbearers (from a completely different Latin root, pallium, a covering, shroud, cloak).
It's pretty clear that appalling trade is the trade of the undertaker/funeral director. The text goes on to mention that Dark Parade (the funeral procession), where Dickinson uses figurative dark = sombre, foreboding, so it seems unlikely she actually wanted the corresponding associations of pale = light = non-serious, frivolous, mood-lifting. I think OP's cited study notes are simply "over-analysis".
