From my point of view this isn't a question about array naming conventions, but a question about how to structure your data. Meaning: Which pieces of information belong together - and why? To answer this question you have to look at both, readability and performance.
From a Java developer's perspective (and you tagged the question also for Java) I'm no friend of multi dimensional arrays, as they tend to result in error-prone index acrobatics in huge amounts of nested for-loops. To get rid of the second dimension in your array, one would create additional objects which enclose the information of one column.
The decision to make is now, which data should be embedded in this enclosing object. In your case the answer is simple: A collection of data about one user makes sense, a list of uncorrelated values for one property for a number of arbitrary users usually does not.
Even if you do not encapsule your data into objects and instead prefer to use multi-dimensional arrays, you should keep these thoughts in mind and see the last dimension of the array (in this case one column) as equivalent to the encapsuling object. Your data structure should be useful at all of it's abstraction levels, and this usually means that you put together what's used together.
