Kelly or Kelly Joint : A heavy square pipe or other configuration that works through a like hole in the rotary table and rotates the drill stem. (Bul 10C, Bul D11)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}