Use RENAME to rename a column using the following syntax:

RENAME <old-name> AS <new-name>

For example:

FROM employees
| KEEP first_name, last_name, still_hired
| RENAME  still_hired AS employed

If a column with the new name already exists, it will be replaced by the new column.

Multiple columns can be renamed with a single RENAME command:

FROM employees
| KEEP first_name, last_name
| RENAME first_name AS fn, last_name AS ln