Mock Welsh was one of the two main languages spoken in NEWI Cefn Druids and Druida (The Druidish Lands), along with English. It is basically a bastardisation of English, where sounds in words are replaced by similar sounding Welsh equivalents. For example, the sound of "th" is often replaced by "dd".
The language was mostly spoken in the north of NEWI Cefn Druids, especially in the Anwir Cymru region in the north east of the country. However, since the Make Druida Sober campaign was such a success, Druidans realised that what they were actually talking was utter gibberish, and so the language died a sudden death. It is now barely spoken.