Leeneia, the etymology of "gricer" has never really been established.

These days it seems to mostly refer to maniacs with cameras who chase steam trains, but historically could be applied to yer average trainspotter and originally meant somebody who tried to get to as many different railways as possible.

There were several articles about this around the end of British steam in the 1960's. One person claimed that it was the plural of "grouse" and had got attached to railfans in the 1930s from their habit of charging through grouse moors and upsetting the birds. I'm not making this up, honest! Later on there were a bunch of guys, some of them at Newcastle University, who had an obsession with getting "the ultimate master shot". A couple of them wrote for the railway press and the term "gricer" got into common railfan usage.

Incidentally, while some of these guys later held extremely responsible positions on the railways and in the preservation movement, in the 1960s they were, shall we say, eccentric. One of them, Paul Riley, who is no longer with us, once got the master shot by climbing about 60 feet up an electricity pylon. The stories are endless and I hope someone (not me!) will collect them and write a best seller.