In response to post no.1 in this thread, it's worth pointing out that there are Junction Indicators (the line of three white lights), and Route Indicators (which are numeric), but the phrase 'Junction Route Indicator' is incorrect.
I'm certain I've seen the term "arbor lights" fairly recently in an ancient publication. The term "arbour" referring to tree. Assume (ignoring railway rule 1, never assume anything) the signal post is the "tree", if there were 5 routes that could be taken, the top of the signal post would look like a tree with 2 indications possible on the left, 2 on the right, with a proceed aspect for straight ahead. The maximum number of routes could be 7! any more than that on the big railway required a numerical indicator.
The term "stick" probably referred to the semaphore signal arm, or on single lines the token or train staff. Board was probably from earlier signals where there was a rotating board on top of a pole. If the driver could see the board he would stop at it. If he didn't see it, he kept going! the last signl like that was actually in operation until fairly recently on the Southam branch from Rugby. It controlled the entry to Bilton Cement Works. the line was operated on the one-train in section principle with a token being kept in the Rugby shunters' bunk. The loco required that to be on the branch. At Bilton a line branched off to the cement works across a main road. The signal was a board mounted on an OHLE lattice post. The board rotated and the driver could see it over the trees. when the shunter had closed the leve crossing gates and the loco pushed the train over the crossing. when the train went "bang" it had hit the works diesel shunter which then coupled to the wagons and took them on into the works. The loco and any other wagons the reversed back onto the branch. The board was turned back and the leve crossing opened to road traffic.