The name is believed to come from the shape of the number "0" being similar to that of a duck's egg. Hence for scoring zero runs is termed as "DUCK".

If a batsman get out on the first ball faced by him is known as "Golden Duck".

If the batsman get out on the first ball of the innings then it is known as "Diamond Duck"

If the batsman get out for Zero in both the innings of the test match it is termed as "Pair".

http://en.wikipedia.org/wiki/Duck_%28cricket%29

The name is believed to come from the shape of the number "0" being similar to that of a duck's egg. Hence for scoring zero runs is termed as "DUCK".

If a batsman get out on the first ball faced by him is known as "Golden Duck".

If the batsman get out on the first ball of the innings then it is known as "Diamond Duck"

If the batsman get out for Zero in both the innings of the test match it is termed as "Pair".

Reference: Wikipedia