What's the provenance of the phrase "bob's your uncle"?

Question

Today I saw in my English class that the phrase "Bob's your uncle" is used to say when the people reach an objective, for example:

My house is in Mexico City, at Eje Central, you go to the Torre Latinoamericana, turn to the left, straight ahead in that street, pass three streets, turn to the right, straight ahead four streets and Bob's your uncle!

Another example would be:

To make hotcakes, you should shake two eggs with 15 oz of flour, mix it with milk, cook them on the stove and Bob's your uncle

My question here is, Why the translation of these phrase is too different with the usage? Is there a legend or a story about that phrase?

Answer 1

First off, I'm American and I had only scantily heard of this idiomatic expression before you posted it here as it is almost never said in the United States; it is apparently common in England, however, and its provenance is unknown, but there are a few possibilities. https://www.phrases.org.uk/meanings/bobs-your-uncle.html

However, I must forewarn you that this is one of those idiomatic expressions that you could only get away with in England. If you asked this in the United States, 99.99% of people would say either, "No, I don't have an uncle named Bob. What are you talking about?" or "Yeah, I have an Uncle Bob. What's your point? That has nothing to do with these directions."

In the U.S., rather than say, "Bob's your uncle", we would simply say, "There you go" or something similar to that. Other things we might say in the U.S. are "presto" or "voila" or "ta-da". I'm just thinking of a few right now that would make sense.