What is an exclamation expressive of sorrow, pity, or apprehension of evil; -- in old writers, sometimes followed by day or white; alas the day, like alack a day, or alas the white called?

alas — An exclamation expressive of sorrow, pity, or apprehension of evil; -- in old writers, sometimes followed by day or white; alas the day, like alack a day, or alas the white. (Webster's 1913.)

Sources