Latin for “you too,” tu quoque a logical fallacy where an incorrect position is defended because the other party is guilty of the same. This is where the “you too” comes from. “Your position is invalid.” “Well, so is yours!” That may be, but it doesn’t change the falsity of your own position. An argument should be divorced from whatever its proponent does or acts on, and be taken on its own merits. For example, a climate scientist might have their work attacked because they themselves burn plenty of fossil fuels. The action of the scientist themselves does not have any bearing on the validity of their research, which should be evaluated on based on the usual criteria, like logical self-consistency, reproducibility, sound methodology, etc.
You can hear this one a lot in many conversations, since it has emotional appeal: “You shouldn’t do that.” “Well, you do it!” “That doesn’t make it right.” An alternative name for this fallacy is the appeal to hypocrisy, and nobody likes a hypocrite.