Actual, recent usage
I encountered a new term recently, referring to a person to be (or has been) baptized: the "baptizand". The context is this 2022 video Rebutting Gavin Ortlund on Baptismal Regeneration (minutes 16:38-17:12) where Gavin Ortlund used the term twice in the same paragraph:
Two of the specific points of emphasis in the Baptist tradition for what God is doing through baptism because it’s not just us show our faith or something, God is at work in it. One is the emphasis upon the gathered community, it’s not just for the [baptizand], it’s for everyone who is gathered. And it’s giving a visible portrait of the Gospel to everyone who is present, and God is communicating grace to those who observe in faith. And so the language of sign and seal that you find throughout the reform tradition, that isn’t just with reference to the [baptizand].
although the transcriber (I think) makes a mistake in rendering it "baptizeined" in the transcript, maybe owing to the rarity of this word in common usage, although I'm pretty sure Gavin got it from recent scholarly books on baptism referenced by Wiktionary. The way Gavin pronounced it validates that he really meant "baptizand" and that he meant it as a technical term since he also used "baptized" a lot, although never "baptizee".
Later on, Gavin used it once more:
It’s really interesting, the whole set of catechetical lectures opens with this warning about Simon the Magician in Acts 8 who’s baptized, and he doesn’t have faith. And it says that basically his baptism does nothing for him. And he’s offering all these warning throughout of basically don’t be a Simon. And he says if you don’t repent, the water will receive you but the spirit will not accept you. And he says this throughout. In lecture three section four, he says, “Neither does he that is baptized with water but not found worthy of the spirit receive the grace and perfection.” Now, this is not going to be a problem for all views of baptismal regeneration but to the extent that you get infant baptism and then a disconnect between the regenerative work of baptism and saving faith in the [baptizand]. These passages are going to require some kind of explanation.
Short of simply emailing Gavin himself, I wonder whether there is a difference in meaning between "the baptizand" and "the baptized"? It is clear that "baptized" means a person already baptized. Maybe "baptizand" refers to a candidate for baptism? Or maybe it is simply to refer to one of the party in the scene of the baptism ceremony?
There is also the word "baptizee". How is it different than "baptizand"? Can I substitute "baptizee" for "baptized"? Or can "baptizee" only be used prior to baptism? Can we thus infer that "baptizee" is different from "baptizand" in that the former doesn't have the "candidate" connotation? Or is "baptizee" interchangeable with "baptizand" as a word pointing to one of the parties in the ceremony?
Is there an etymological connection between the three, or regional variations in which the three terms are used?