Contrived British acronym dating back to the 1950s or so for a pedestrian light controlled crossing, by analogy with the earlier zebra crossing. In other words, a pedestrian crossing where you press the button and wait for the green man.

The zoophilia of Brish highway engineers has continued on the same lines to give us others including the puffin crossing (pedestrian user-friendly intelligent signals - with automatic detection of pedestrians instead of the push button) and the toucan crossing for combined cycle paths and footways (two can cross at the same time, see?)