Etymology of railway terminology

clive in post 159569 said:

You've got "arbour lights" where the rest of us have feathers, of course. Was there ever a special name for when the lights were between the home and distant heads? (The best-known example of that was one of the eastbound starters at Earl's Court, but I'm sure I've seen others.)

I can only think you are referring to a repeating signal for the arbour lights/junction ahead, which is just known as a "junction repeater" and on explaining what it showed would no doubt be described as "a repeater of the main signal with or without the arbour lights"

Anothersignalman in post 159416 said:

Steamer in post 159384 said:

Anothersignalman in post 159381 said:

Were plunger locks a thing in the UK?

The GWR (and possibly others) went down that route, where the electric lock was released by pressing a plunger before moving the lever.

Different type of plunger, might be a local terminology thing. I meant the hand-worked plunger lock that was fitted to mainline turnouts at non-interlocked locations, where home signals were mechanically detected and worked by any one of a series of quadrant levers. This system is still in use at Emerald and Cockatoo on the Puffing Billy line, and was used on the suburban terminus Hurstbridge until maybe a decade ago.
Examples:
https://railgallery.wongm.com/signalling/E116_7181.jpg.html
https://railgallery.wongm.com/victorian-goldfields-railway/F133_5753.jpg.html
https://railgallery.wongm.com/south-gippsland-railway/F139_6684.jpg.html
https://railgallery.wongm.com/signalling/E105_0810.jpg.html

Yes, definitely different. The plungers we're talking about were electric push-buttons, usually brass (sometimes with a brass housing or sometimes plastic) and - in a well-kept box - highly polished and only ever pressed with a duster. A couple of brass ones shown here https://signalbox.org/photo-gallery/london-south-western-railway/romsey/