The letter "L"
Stands for Loser or Lester, the number 1 heist master.
Person 1: hey look its L
Person 2: Lester or Loser
Person 1: he's just a Loser
Person 2: so he's The letter "L"
Person 2: Lester or Loser
Person 1: he's just a Loser
Person 2: so he's The letter "L"