This is an English expression which is commonly used in a metaphorical context and primarily in informal situations.
This expression is used to suggest that someone is in a bad mood and is unusually grumpy. The use of this expression suggests that there is no reason for the person to be in a bad mood and that they have simply got out of bed feeling that way.
This expression dates back to Roman times when it is said to have been bad luck to get out of bed on the left hand side as this would mean that your day would not go well. The superstitious nature of the left hand side in Roman times was common. For example it was said to be bad luck to put your left shoe on first or to walk into a house with your left foot in front of your right.
The phrase is also sometimes said as “to wake up on the wrong side of the bed” to have the exact same meaning.
An example of the usage of this expression can be found in a quote from American novelist, Tom Robbins in Still Life With a Woodpecker. The quote reads “Albert Camus wrote that the only serious question is whether to kill yourself or not. Tom Robbins wrote that the only serious question is whether time has a beginning and an end. Camus clearly got up on the wrong side of bed, and Robbins must have forgotten to set the alarm.”