E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
He tirléd at the pin. He twiddled or rattled with the latch before opening the door. Guillaume di Lorris,
in his Romance of the Rose (thirteenth century), says, When persons visit a friend they ought not to bounce all at once into the room, but should announce their approach by a slight cough, or few words spoken in the hall, or a slight shuffling of their feet, so as not to take their friends unawares. The pin is the door-latch, and before a visitor entered a room it was, in Scotland, thought good manners to fumble at the latch to give notice of your intention to enter. (Tirl is the Anglo-Saxon thwer-an, to turn; Dutch dwarlen, our twirl, etc.; or Danish trille, German triller, Welsh treillio; our trill, to rattle or roll.)