The 1st edition Player's Handbook had an 'acrobatic' rogue class, with various jumping, tight-rope walking, and tumbling abilities. In the 2nd edition PH, the abilities of the acrobat were broken up into proficiencies -- all the abilities, save one. The final ability conversion to AD&D (2nd edition) is the falling proficiency. Thus, a character with the jumping, tumbling, tight-rope walking, and falling proficiencies would be able to perform as per the 'acrobat' from the 1st edition guide.
This allows a character to fall up to twenty feet, and, upon a successful check, take no damage. Each successive slot spent in falling allows the character to fall an additional twenty feet (though only one check is necessary).
Characters with a Dexterity score of 17 or higher can fall an additional five feet per slot (including the first one), and characters with an 18 Dexterity can fall an additional ten feet per slot.
Previous Proficiency of the new Proficiencies