I came across this phrase twice while reading the play Merchant of Venice by William Shakespeare in the following contexts:
1 - "Out upon it old carrion, Your flesh rebels at these years?". A character Solanio is mocking the Jew Shylock by asking sarcastically if he is still having sexual urges at this age.
2 - "Out upon her! Thou torturest me". Shylock's daughter Jessica stole money from her and Shylock is speaking to another Jew and is probably insulting her in this particular line.
Both times, the phrase is used following a negative backdrop, and I suspect its some sort of an insult in medievalold English. Any clarification would be helpful.