SQL union for one identical column

CREATE TABLE IF NOT EXISTS `test` (
  `idtest` INT NOT NULL AUTO_INCREMENT,
  `label` VARCHAR(45) NULL,
  `translation` VARCHAR(45) NULL,
  `language` VARCHAR(45) NULL,
  PRIMARY KEY (`idtest`))
ENGINE = InnoDB

insert into test values (1, 'lbl1' , 'NAME', 'English');
insert into test values (2, 'lbl1' , 'N4M3' , 'EnglishCustom');

SELECT COALESCE(t2.translation,t1.translation)
FROM test t1
  LEFT JOIN test t2
         ON t1.label = t2.label
        AND t2.language = CONCAT (t1.language,'Custom')
WHERE t1.language = 'English';