"You're too fucking polite, Malfoy," Goyle says, once, in a rare moment of bravery. Draco gives him a long-suffering look, and none of the Slytherins bring it up again while he's around. It's not as if it's important, what Draco says or doesn't say.
Polite
by V
Draco learned to swear at a young age. He's heard, countless times,
his father yell at -- whoever happens by and tests his anger, it
doesn't matter. Draco has always thought the words sounded ugly and
twisted as they feel from his father's lips: they were merely
venomous words without meaning and without purpose. For this, he
doesn't curse.