Coal-mining. [f. THROUGH prep. or adv. + -ER1.] (See quots.)
1797. Encycl. Brit. (ed. 3), V. 101/1. The workings called rooms … of the width of 12 feet;… the workings called throughers or thirlings, 9 feet wide, wrought through at right angles from one room to another.
1883. Gresley, Gloss, Terms Coal Mining, Througher,… a thirl put through between two headings which are up-stoop.
