Concise Bible Dictionary:

A spring on the border of Judah and Benjamin. It was where Jonathan and Ahimaaz stayed in secret, to carry to David any message from Hushai, on the revolt of Absalom; and close to this spring Adonijah called the king’s sons together when he exalted himself to succeed David as king (Josh. 15:77And the border went up toward Debir from the valley of Achor, and so northward, looking toward Gilgal, that is before the going up to Adummim, which is on the south side of the river: and the border passed toward the waters of En-shemesh, and the goings out thereof were at En-rogel: (Joshua 15:7); Josh. 18:1616And the border came down to the end of the mountain that lieth before the valley of the son of Hinnom, and which is in the valley of the giants on the north, and descended to the valley of Hinnom, to the side of Jebusi on the south, and descended to En-rogel, (Joshua 18:16); 2 Sam. 17:1717Now Jonathan and Ahimaaz stayed by En-rogel; for they might not be seen to come into the city: and a wench went and told them; and they went and told king David. (2 Samuel 17:17); 1 Kings 1:99And Adonijah slew sheep and oxen and fat cattle by the stone of Zoheleth, which is by En-rogel, and called all his brethren the king's sons, and all the men of Judah the king's servants: (1 Kings 1:9)). It was no doubt a spring not far from Jerusalem. Bir Eyub, about half a mile south of Jerusalem was long supposed to be the spot, but this is a well, not a spring. The Fountain of the Virgin, near the south east corner of the city, is now more generally chosen; but this appears to be too near the city to coincide with the above events.

Strong’s Dictionary of Hebrew Words:

from 5869 and the active participle of 7270; fountain of a traveller; En-Rogel, a place near Jerusalem: --En-rogel.

Jackson’s Dictionary of Scripture Proper Names:

fount of the spy

Potts’ Bible Proper Names:

Fountain of the fuller; fountain of a traveler:―place near Jerusalem, Josh. 15:7. {Fons fullonis}