What does the phrase 'which end is up' mean?

[Priya Raghavan]

English Language Tests, Intermediate level

ESL/EFL Test #284 "English Slang Idioms (6)", question 5

The judge decided that in his opinion, the new lawyer didn't know which ......... was up. He made several rookie mistakes and didn't seem to know what to do next.

(a) end
(b) side
(c) stock
(d) trend

English Language Tests, Intermediate level

ESL/EFL Test #284 "English Slang Idioms (6)", answer 5

The judge decided that in his opinion, the new lawyer didn't know which end was up. He made several rookie mistakes and didn't seem to know what to do next.

Correct answer: (a) end

Your answer was: incorrect
The judge decided that in his opinion, the new lawyer didn't know which side was up. He made several rookie mistakes and didn't seem to know what to do next.
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What does the phrase 'which end is up' mean? Would like to know the origin as well, if possible. Is this similar to 'which side of the bread has the butter'?

Priya Raghavan

[Daemon99]

It means confused

If you don't know which end is up, you are confused.
No, it is not the same as "which side of the bread has the butter".
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Non-native speaker of English
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I intend to live forever - so far, so good.

[Benjamin]

Hi it means confused, like daemon says
it implies that if they had a box, for example, they wouldn't know which was the top and bottom and wouldn't know how to hold it etc.

there is also another expression
"doesn't know his arse from his elbow"
VERY informal
but again...is so useless and confused that if he was shown a picture of his bum or elbow, he wouldn't know which was which (i.e. he was VERY useless)

i think i could've explained that better...sorry