tribulum

(from the article `agriculture, origins of`) ...ears as the vehicle was pushed through the crop. The grain was threshed in the long-established way, by animals treading it on a firm floor, or by ...
Found on http://www.britannica.com/eb/a-z/t/78

Tribulum

(Latin) wooden sled pulled over wheat to separate the chaff.
Found on http://www.hestories.info/greco-roman-world-glossary.html
No exact match found