The National Trust walks mentioned in this article do not appear to be on their website. I did, however, find a short walk visiting Pisser Clough, elsewhere on the web:
This link does not mention the famous name, but the map clearly shows Pisser Clough, Pisser Hill and Pisser Rough.
The name Pisser Clough can apparently be traced back to shortly after the Norman Conquest:
Pisser Clough was discussed on Women's Hour on Radio 4 some time ago, along with other odd placenames. A local West Yorkshire historian traced the name back to a barony boundary map on which three cloughs were itemised in near proximity to each other ("clough" might sound like it could have come from the Gaelic "cloch" - stone - but there is no reason to surmise Gaelic connotation in Yorkshire, which leaves the standard interpretation of "wooded vale" as the logical choice of meaning, whatever the supposed etymology). Each clough was listed with a comparative description based on size and the lesser of the three was marked as "pissen". Since the boundary map was from early post-conquest it is a fair assumption that "pissen" was simply a rendition of the French "pissant", meaning insignificant or least significant.
Pisser Clough is indeed rather unimpressive, but the path over it turns out to be very interesting. There is no signpost on the Widdop Road, and the start point is difficult to find, but the path is not difficult to follow after that. It is, however, precarious in places, with a steep drop on one side. It also has a collapsed bridge, and the bridge over Pisser Clough itself has seen much better days. The scenery is very good, however.
I met three men working at the end of the path. They told me that I was the first person they had seen for three days. Despite its fame, Pisser Clough is not much walked.
The path onward through Greave Pasture is not marked, and there is no path on the ground. It is also rather heavy going, and the views are not especially good. It is better to continue via the track to the Calder / Aire Link.