Chapter 9 Query Language Reference : Reserved Words

Reserved Words
The following key words are used by the object query language.
 
Escaping the Keywords
You cannot use key words as identifiers, resource names, or folder names without prefixing them with the # escape character.
Examples:
select id from /#Order o
select /#DateTime/format(birthDate, "yyyy-MM-dd") from /Person
select e.sender as #from from /Email e