A nickname is like a special name that your friends or family give you that is different from your real name. For example, if your name is Sarah, your friends might call you "Sari" as a nickname.
A lot is a word we use to talk about many things or a big amount of something. For example, if you have a lot of toys, you might have ten or more toys.
Now, when we put these two things together, a nickname for "a lot" might be "lot". This can mean having a big amount of something, like if you have a "lot" of candy, you might have a whole bag full.
Some people might use the nickname "lot" to describe someone who has a lot of something, like a friend who has a lot of clothes or a lot of books. It's a fun way to describe someone without using their real name.