This episode's title "From Unknown Graves" is a quote from the abolitionist poet Henry Wadsworth Longfellow's poem, "The Witnesses", from his book "Poems on Slavery". Specifically the final stanza: These are the woes of Slaves;
They glare from the abyss;
They cry, from unknown graves,
"We are the Witnesses!"
The specs for the new "4th generation" quantum drive introduced this season are given, with the speed rating of 17 light years per hour, a great increase from the previous 10 light years per hour.
First appearance of the Janisi, who were previously mentioned in All the World Is Birthday Cake (2019).
The name of the matriarchal species the Janisi sounds close to the word gynaeceum, which refers to women's quarters in Ancient Greece and Rome.
This is hinted at during the Star Trek: TNG 209. "Measure of a Man" Building a race of robots/androids (Datas) to work as slaves.