Llwk-Yu
The Llwk-Yu river is the main watercourse running through Llamedos, and passes to the sea through the capital city of Pant-y-Girdl. The port here has been expanded to allow for a greater volume of barge trade from the river, and for a greater level of import-export trade with Ankh-Morpork.
Annotation
The spelling has been maintained as used in The Compleat Discworld Atlas, but in the interests of pedantry and slight irritation, it should be pointed out that there is no letter "k" in the Welsh language (used as a referent for Llamedosian). A more accurate spelling might be Llwc-Yw, as in yr afon Llwc-Yw, to fit with Welsh phonetics and alphabet. The "c" is always hard: as in the Flintshire placename "Y Bwcle", "Buckley" in English.
It is pronounced as "look you", which is a stereotyped Welsh interjection.