The phrase is thought to have originated in the 19th century, when it was used by gamblers to refer to a bet that was sure to lose. Over time, the phrase has come to be used more generally to mean anything that is worthless or of little value.
Some people believe that the phrase "for birds" is offensive, as it can be seen to suggest that birds are worthless or unimportant. However, it's important to note that the phrase is not typically used in a derogatory way, and is more often used to express a sense of frustration or disappointment.