oubliette
Starts with a e
Springfield made a 20ga trapdoor called the Foragers. There is a 12ga trapdoor out there called the "Zulu Snyder". They were converted French Mle 1857 percussion rifles converted to an 1867 breech loader and then converted into a smooth bore 12 ga.
A dark underground prison is called a dungeon. These were very popular in the medieval era, due to the difficulty of escaping, and relative ease of maintenance. A prisoner would have to escape up several floors past guards and other residents of the fortress/castle in order to escape. Alternatively, a prisoner could get out through an underground passage, but these were very rare, and often were unstable.
The window in a ceiling or roof is called a Skylight.
the trapdoor of the larynx is the epiglottis
Through the Trapdoor.
Spiders.
They are located west of the Lumbridge general store in some ruins ( Known as the H.A.M Base ). To open the trapdoor, players need to pick the lock on it with their Thieving skill. They can do this by hand, but a lockpick will increase the chance of success. On the trapdoor entrance to the dungeon, there is an actual ham which may be a spoof towards their name and possibly color.
your trapdoor was made in 1883
yes it had a dungeon somewhere on the western side of the site accessed only by a trapdoor in the roof. (according to this website http://www.history-tourist.com/V2/england/corfe-castle_S0136.html)
Ceiling Mount Traverse Rod
Trapdoor spiders are arachnids not insects and they are inverts.