1) An Old English word meaning ‘hole’ or ‘aperture’, linked etymologically with ‘through’: as a verb it meant ‘to make a hole’.
It has survived in some dialects but is not now in general use, although many people are aware that ‘nostrils’ means ‘nose holes’: the spelling ‘nose therlis’ in Wyclif’s translation of the Bible illustrates the development./br>Both the noun and the verb have already been identified as part of the national mining vocabulary but not earlier than 1686. Wright comments on the word’s popularity in some mining communities, and from a Cheshire source of 1878 quotes: When a man has … made an opening or connection between a new and old working, he is said to have thirled. In fact, a south Yorkshire mining lease of 1486 contains three examples of the word’s use, referring to a coal pit now of new thyreled and with clauses in the agreement which required the lessees to drive a head with post and thyrle in order to drain the mine. Finally they were to keep a ribbe … unthyreled, Cortworth. There are references later in the accounts of the Farnley colliery near Leeds although the precise interpretation in this case is less clear cut: 1711 the Thurle 2 dayes and earth feying
1718 Gotten in the Thirle by the Levell gate. Much more explicit is an entry in the diary of Ann Lister: 1833 7 yds distance from the great horizontal shaft runs the windgate from which air is conveyed into the great shaft by thirls at about 25 to 30 yds from each other, Halifax. In this instance ‘thirling’ was clearly a way of ventilating the pit.