Looking to understand what the r in _rTotal and t in _tTotal means

I am new to Solidity and contracts. Have a background in JavaScript and been spending hours into learning Solidity and reading multiple contracts.

I was hoping to gain some insight from those with experience. It is a lot of fun to read this and try to piece the puzzle together on how it all works but I was wondering what does an r and t refer to in front of variables?

Example:

uint256 private _tTotal = 1000000000 * 10**6 * 10**9;
uint256 private _rTotal = (MAX - (MAX % _tTotal));

or

mapping (address => uint256) private _rOwned;
mapping (address => uint256) private _tOwned;

I wish people used the full word in order for those starting can actually understand if t refers to Transfer or something else.

Thank you for everyone who can help me understand this and looking forward to diving into this :smiley: