Concise Bible Dictionary:

2. rosh, χολή, some exceedingly bitter or poisonous plant not definitely identified. This word is used as symbolical of “bitterness.” To turn to idolatry was like “a root that beareth gall and wormwood” (Deut. 29:1818Lest there should be among you man, or woman, or family, or tribe, whose heart turneth away this day from the Lord our God, to go and serve the gods of these nations; lest there should be among you a root that beareth gall and wormwood; (Deuteronomy 29:18)). God’s judgments were given them as water of gall to drink (Jer. 8:1414Why do we sit still? assemble yourselves, and let us enter into the defenced cities, and let us be silent there: for the Lord our God hath put us to silence, and given us water of gall to drink, because we have sinned against the Lord. (Jeremiah 8:14); Jer. 9:1515Therefore thus saith the Lord of hosts, the God of Israel; Behold, I will feed them, even this people, with wormwood, and give them water of gall to drink. (Jeremiah 9:15); Jer. 23:1515Therefore thus saith the Lord of hosts concerning the prophets; Behold, I will feed them with wormwood, and make them drink the water of gall: for from the prophets of Jerusalem is profaneness gone forth into all the land. (Jeremiah 23:15); compare Deut. 32:3232For their vine is of the vine of Sodom, and of the fields of Gomorrah: their grapes are grapes of gall, their clusters are bitter: (Deuteronomy 32:32); Lam. 3:5,195He hath builded against me, and compassed me with gall and travail. (Lamentations 3:5)
19Remembering mine affliction and my misery, the wormwood and the gall. (Lamentations 3:19)
; Amos 6:1212Shall horses run upon the rock? will one plow there with oxen? for ye have turned judgment into gall, and the fruit of righteousness into hemlock: (Amos 6:12)). Gall, mixed with the sour wine or vinegar drunk by the Roman soldiers, was given to those about to be crucified, for the purpose, as is now supposed, of making them the less sensitive to the torture. It was offered to the Lord, but refused (Psa. 69:2121They gave me also gall for my meat; and in my thirst they gave me vinegar to drink. (Psalm 69:21); Matt. 27:3434They gave him vinegar to drink mingled with gall: and when he had tasted thereof, he would not drink. (Matthew 27:34)). In Mark 15:2323And they gave him to drink wine mingled with myrrh: but he received it not. (Mark 15:23) myrrh is read instead of gall; the meaning would be the same.