A CSGO Youtuber from A̶u̶s̶t̶r̶a̶l̶i̶a New Zealand with a bunch of faggot friends that got successful thanks to one dude talking about taco children... I'm not jealous.
"You watch that Fitz video yesterday man?"
"DON'T TAKE MY KIDS MAN! NOT SPICEY!!"
Means "son of" (hence all the English surnames like Fitzpatrick, Fitzhenry) but can also refer to an illegitimate child, a bastard, someone born out of wedlock etc.
FitzChivalry is the illegitimate son of Chivalry, the heir to the throne of Buckkeep.