E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Sadlers Wells (London).
There was a well at this place called Holy Well, once noted for its extraordinary cures. The priests of Clerkenwell Priory used to boast of its virtues. At the Reformation it was stopped up, and was wholly forgotten till 1683, when a Mr. Sadler, in digging gravel for his garden, accidentally discovered it again. Hence the name. In 1765 Mr. Rosoman converted Sadlers garden into a theatre.