Both Uses

revelation
in
The Great Gatsby
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Most of the confidences were unsought — frequently I have feigned sleep, preoccupation, or a hostile levity when I realized by some unmistakable sign that an intimate revelation was quivering on the horizon; for the intimate revelations of young men, or at least the terms in which they express them, are usually plagiaristic and marred by obvious suppressions.
p. 2.1

revelation = something previously unknown; or making such a thing known
Most of the confidences were unsought — frequently I have feigned sleep, preoccupation, or a hostile levity when I realized by some unmistakable sign that an intimate revelation was quivering on the horizon; for the intimate revelations of young men, or at least the terms in which they express them, are usually plagiaristic and marred by obvious suppressions.†
p. 2.1 *

Definitions:

(1) (revelation)
something that was previously unknown (and typically surprising); or making such a thing known
(2) (meaning too rare to warrant focus)
As a proper noun, Revelation refers to the last book of the Bible with visionary descriptions of the End of Days. It can also refer to things revealed religiously rather than via logic.