Llamedos is ‘sod em all’ backwards. This is a reference to the town of Llareggub in Dylan Thomas’ short prose piece Quite Early One Morning. That story was later expanded into Under Milk Wood, a verse play scripted for radio. In that version the name of the town was changed to the slightly less explicit Llaregyb.
Apart from that, Llamedos is instantly recognisable to the British as the Discworld version of Wales. The double-l is a consonant peculiar to the Celtic language (from which Welsh is descended), hence also Buddy’s habit of doubling all l’s when he speaks.