batch – SOQL: First error: missing value at ‘FirstName’

The SOQL string you are creating is missing spaces so instead of valid SOQL:

... FROM Account WHERE FirstName LIKE 'REDACTED%'

the SOQL string you are generating is:

... FromAccountWHERE FirstName LIKE'REDACTED%'

Also an Account does not have a FirstName field.

I would use code like this to make the spacing more obvious in the SOQL expression:

String soql = String.format(
    'select Id, Name from {0} where FirstName like {1}',
    new Object[] { strObjectName, aName }
});
return Database.getQueryLocator(String.escapeSingleQuotes(soql));

and the escaping is to avoid the SOQL Injection risk.