The title refers to diamond gemstones with the highest quality, having, or approaching, the clarity, purity, and perfection of clear water. It is also used to describe an exceptionally beautiful young woman.
In the books, the Berbrooke men were used as comic relief and the Bridgerton girls were never encouraged to marry them or encourage them.
The mansion under construction is Carlton House.
The song playing during the ball is a string arrangement of Arianna Grande's "Thank U, Next."
Kris Bowers' score was composed and performed completely remotely during the course of the Covid-19 pandemic. The score is largely comprised of orchestral versions of contemporary hits, not music of the period.