Vinegar

Heb. hometz, Gr. oxos, Fr. vin aigre; i.e., "sour wine."
The Hebrew word is rendered vinegar in Ps. 69:21, a prophecy fulfilled in the history of the crucifixion (Matt. 27:34). This was the common sour wine (posea) daily made use of by the Roman soldiers.

They gave it to Christ, not in derision, but from compassion, to assuage his thirst. Prov. 10:26 shows that there was also a stronger vinegar, which was not fit for drinking. The comparison, "vinegar upon nitre," probably means "vinegar upon soda" (as in the marg. of the R.V.), which then effervesces.