A mistaken King James Version translation of a Hebrew word that was the name of a Canaanite goddess, Asherah. Often, sacred trees were symbols of that fertility goddess. Sometimes, wooden poles were set up. God commanded the Israelites to destroy those symbols. They were called "Asherim" and "Asheroth."
They had to cut them down and burn them (Exodus 34:13; Deuteronomy 12:3). The poles were wooden and did not leave remains that could be identified. However, researchers discovered a large piece of carbonized wood lying between incense burners at an early sanctuary in Ai. It may have been a tree trunk from which the branches had been trimmed. Some researchers suggest it was an Asherah pole.
God strictly forbade the Israelites to worship Asherah or to build her sacred symbols. From time to time Israel disobeyed God and engaged in false worship. One account of the northern kingdom's downfall blames it on groves and the worship of the pagan goddess and her male counterpart, Baal (2 Kings 17:7–18). Jezebel, a priestess of the Tyrian Baal, promoted the spread of such idolatry.
The “grove” of Genesis 21:33 in the King James Version was actually a tamarisk tree.