I have come across two opinions on this:
This was his actual name
His actual name was Suyodhana and he was later on known as Duryodhana.
What was Duryodhana's actual name?
Hinduism Stack Exchange is a question and answer site for followers of the Hindu religion and those interested in learning more about Hinduism. It only takes a minute to sign up.Sign up to join this community
Both are names for the same person and often used interchangeably. Suyodhan means one who is good with arms (in warfare). Duryodhan means unconquerable warrior. Naturally there can be many who are good in battle but there can be only ONE who is unconquerable, by definition. Duryodhan was more unique and it stuck.
Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.