The name that you choose for your vector may be a single character (such as X) or a word (such as data) but you are allowed/encouraged to be more creative. It may be a more or less abstract sequence of letters and numbers (dataEXT2), a combination of words separated by (a) period(s) (My.Precious.Data) or underscore (My_Precious_Data), etc. You are allowed to use upper and lower case; this implies that vector names are case-sensitive, which means that Data and data do not refer to the same vector. Note that names should NOT contain any space or dash (My Data and My-Data are thus not to be used).
Friendly warning: don’t choose names which are way too difficult or abstract, or too long… Indeed, when you will have to handle and recall a dozen of these difficult names, you will certainly start making mistakes and regret your choices.