Bob’s your uncle is an idiomatic phrase, especially prevalent in Britain and Ireland, with a similar meaning to “as simple as that” or the French “voilà”.
It can be referred to as the British equivalent of “piece of cake”.
The origin of the expression is widely claimed to lay its roots in 1887, when the British Prime Minister, Robert Gascoyne-Cecil named his nephew, Arthur Balfour Chief Secretary of Ireland.
“Bob’s your uncle” is said to have been conceived after Balfour referred to the Prime Minister as Uncle Bob.
This origin, however is unsupported as the first documented case of the phrase didn’t appear until 1924.
“Bob’s your uncle” would appear in the 1931 song “Follow Your Uncle Bob” written and composed by J. P. Long and sung by Florrie Forde.
The expression would see widespread usage on the British Isles following the 1940’s.