Why does Alan get the nickname squid in the book holes?

In the book "Holes" by Louis Sachar, Alan gets the nickname "Squid" because of his habit of squirting his toothpaste onto the bedposts of his bunk. This behavior resembles a squid squirting ink, hence the nickname. Additionally, Alan's real name is not revealed until later in the story, adding to the mystery and intrigue surrounding his character.