The main objective of your terminology is to help players understand the game. Thematic concerns are secondary.
Just because Magic calls your deck the library, and your discard pile the graveyard, it doesn't mean you should. Magic is a game with a huge amount of depth and complexity.
Do not use jargon for existing concepts that have an ordinary English word for them. Your deck is just a deck of cards, no matter how much you try to spice it up, by calling it the "archive", "spell book", or "army".
Create jargon when you create a new entity, such as a second deck. However, your jargon should be minimally creative. Its overwhelming objective should be that the greatest number of people correctly understand it. Use whatever word fits that objective best. Tell people a concept, and then ask them what they'd call it.
I like to use neutral terms like location, person/character and board wherever possible. This is even more important when you have varying types of that thing. I don't want to have to remember which guys are "allies", which are "mercenaries" and which are "heroes".
However, you should avoid using known concepts, from classic games. This includes words like joker, wild, and run. These are themeless and immersion-breaking, reminding the player that they're actually just moving bits around, and not participating in an exciting world.
In Egypt-themed Egizia, there's a worker with a white skirt. He's the only worker that can add his strength to another worker. The game calls him the "joker". When I teach people the game, I call him the "helper". It's far more explanatory, and is thematic.
My publisher renamed Radlands' locations to Camps, and citizens to Punks. These added theme, but were not confusable.
Do not include Magic terminology like target (something of your choice), resolve (happen), or Dungeons & Dragons terms like 3d6 (three six-sided dice.) Don't say things like "active player" or "orthogonal" (adjacent, but not diagonally.) Game enthusiasts know these terms. No one else does.
Remember that things like search your deck, and reveal a card, are unknown concepts to many people.
I avoid the terms supply and bank to refer to unused tokens or resources. People don't need to be told that unused pieces should just sit in a pile on the table, and they know that when they gain something, they get it from that pile (not from another player, for instance.)
Do not create a named "zone" for everything, that you refer to, and that players will need to remember. Things can just be "in play" or "on the table" instead of "in the battle zone".
Cards on the table, but not in play, can just be "set aside".
As with jargon, the phraseology you use (typically on cards) should simply be that which conveys the correct meaning to the most people.
The Magic card Dead Ringers reads "Destroy two target nonblack creatures unless either one is a color the other isn't." Basically, the two creatures have to be exactly the same colour or combination of colours, and not black. This card is legendary for its incomprehensibility.
You do not get any extra points for being technically correct. Only huge games like Magic need exact terminology, because they have complicated rules, and are always creating new cards.
You can be very conversational in the language you use on your cards, as long as people know what you mean. You can also be redundant.
A camp in Radlands once had the text "You can only use this ability in a turn in which you play no other abilities." Basically, it must be the only ability you use in a turn.
If you analyse it, there are temporal problems with this strange wording. When you use it, you don't technically know whether it's valid to use it or not, as you're not yet sure whether you'll use another ability later in the turn. Technically, the card's text should tell you that you can only use it if you haven't played any abilities this turn, and it should prevent you from using any further abilities this turn. Despite this technical error, everyone understood the card. There was never a problem.
If anyone is failing to understand something, it's your problem.
It's fine to put explanatory text on cards. Just some small, grey text, that people don't have to read, but that people can refer to if they get confused.
My gangster game contained a card called "Stash". This put two money tokens on the location that the player to your right is on.
Everyone understood what the card did, but no one understood why they'd want to play it. It just seemed wacky and useless.
To me, it was obvious. I play the card, and I put two money tokens under the player to my right. On their turn, they move off that space. I'm the next player around the table, so I'll be the first player who's able to move onto that now-free space, and collect the money.
Even competent gamers didn't understand this card.
The card now has the same text, but at the bottom of the card, there is a small line of text saying: "(Hint: Go there next turn, and collect it.)" Now, everyone understands the card.