The father of Your English, Tim Bowen, gifts us with the mother of all articles on idioms.
The former president of Sony, Norio Ohga, was credited with developing the compact disc and was known as ‘the father of the CD’. If you are the father of something, you are the person who started something or first did it successfully, as in ‘He is often seen as the father of British television comedy’.
Used in a similar way, the expression the mother of is not normally used with people but rather with institutions to denote the first institution of its type, as in ‘The British parliament is sometimes known as the mother of all parliaments’. Unfortunately, although the expression is commonly used, it does not coincide with the facts as the Icelandic parliament is a much older institution. Usually in American English, the word granddaddy (with two double d’s in American spelling) can be used in a similar way to denote the oldest or most famous example of something, as in ‘The Dow Jones, the granddaddy of Wall Street indexes’.
The expression the mother of can also be used to emphasise that something is very big, serious or exciting, as in ‘That was a mother of a storm!’ or ‘The mother of all battles took place here in 1683’.
If someone is described as ‘like a brother to me’, it means that a person is such a good friend that they are almost a family member. Again in American English, the word brother can be used as an interjection to show that you are surprised or annoyed, as in ‘Oh brother, what a mess!’
The expression Bob’s your uncle and Fanny’s your aunt! usually shortened to just Bob’s your uncle! can be used to refer to something that is very quick and easy, as in, ’you just click on the button and Bob’s your uncle the goods will be with you the next day.’
To keep mum means to keep quiet about somthing, and when we want someone to keep something a secret, we can use the expression Mum’s the word, as in, ’We are orginising a party for her but want it to be a surprise. So, remember, mum’s the word.’