It stands for the Dalai Lama, the spiritual
head of Tibetian Buddhism in
Cantonese. The same word is also used to represent a foul word in Cantonese meaning "I Fucked Your
Mum".
Teacher: Swearing is not allowed in the classroom, students!
Student: Dllm 8745
Teacher: What did you
say?
Nerd: Teacher, didn't you know that the Dalai Lama is the spiritual
head in the Tibet Autonomous Region?