In his 1607 Rich Storehouse, or Treasurie for the Diseased, Matthew Blower offers “a present medicine for the hickop”:

Take thy finger ends, and stop both thine ears very hard, and the hickop will surcease immediately.

I found this in Julian Walker’s How to Cure the Plague and Other Curious Remedies (2013), a collection of historical cures for various maladies. He says, “I tried it, and it worked.”