which somber garb singularly set off very fair necks and faces

[Irelia20150604]

The quotation comes from Charlotte Brontë – Jane Eyre (Chap. 28) | Genius

Quotation: Two young, graceful women—ladies in every point—sat, one in a low rocking-chair, the other on a lower stool; both wore deep mourning of crape and bombazeen, which somber garb singularly set off very fair necks and faces: a large old pointer dog rested its massive head on the knee of one girl—in the lap of the other was cushioned a black cat.
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Hi everyone! I don't quite understand the bold part, especially the word "which". What does the word refer to?
My interpretation is as below:

to set off => 1. c : to set apart : make distinct or outstanding [M-W dictionary]
singularly => extraordinarily
the sentence => somber garb extraordinarily made very fair necks and faces distinct. (the word "which" seems redundant)

 

[Minnesota Guy]

Your understanding of the passage as a whole is correct!

The use of which is correct, but unusual. It seems to function both as a relative pronoun, and as an adjective modifying somber garb. You could paraphrase it as "a somber garb which singularly. . . . ." (Hope that makes sense!)

Set off here means "to intensify the look of by contrast or by emphasizing different colors, etc."

 

[Irelia20150604]

Ah, I see! Thank you for your explanation!

 

[GreenWhiteBlue]

I disagree with Minnesota Guy. "Which" refers back to "mourning" (which here means "black clothing worn as a sign of mourning". You could leave out "somber garb", and still have the main idea: the two ladies wore mourning, which emphasized how pale their complexions were. "Somber garb" is another way repeating the idea of "mourning". Here are other examples of "which" used the same way (that is, referring back to something named in the previous clause, and followed by a term that identifies that same thing with a different term):

I gave him $200, which amount will serve as a final payment for the debt.
The school received books, pens, and laptops, which items will be distributed to the students.