And now, a few place-names:
Brokilon - The forest-land of the Dryads, possibly inspired by the marvellous Forest of Broceliande (various spellings), which figures into Arthurian romance and Breton folklore. Notably, it was the wood in which the wizard Merlin was enchanted by his lover and apprentice, the deceiving sorceress Vivien, or Nimue. Unfortunately, I was unable to find an entirely satisfactory etymology for this name, beyond roots in Breton Celtic.
Ellander - The duchy within Temeria, where the healer Nenneke makes her home, similar in appearance to the modern German word Elend, 'misery, distress, or poverty', (an Elender being a 'wretch', or 'miserable person'), with an original meaning akin to 'outland', or 'exile'. Given that Geralt's misery, and wounds, are tended in Ellander, the connection is not impossible.
Lyria - One of the realms ruled by Queen Meve, the name bears striking resemblance to the word lyre, the musical instrument, and its derivatives lyric, lyrical, etc. The etymology is a bit complex, but the Greek word for lyre, lura, may be linked to the act of lauding, or praising, in this case in song, accompanied by the lyre. Lyria has a reputation as a pleasant land, thus this could be a reference to its praise-worthy qualities, or simply evoke the idea of lyrical music, scenery, and luxury.
Rivia - The other realm ruled by Queen Meve, possibly related to the word river (akin to Latin rivus), or from the archaic English verb rive, 'to rend or tear' (as in riven). I incline towards this latter, especially since the German version of the name is Rivien, and the capital Riva, which is mildly suggestive, it is identical to the Old Frisian form of rive. Also, since Lyria and Rivia are twin realms, the concept of one of them bearing a name meaning 'torn' or 'separated' does not seem too far-fetched.
Temeria - Based on King Foltest's various amorous alliances, I think it likely that the kingdom's name could derive from the Latin verb temerare, meaning, 'to violate (sexually), defile, or pollute'. Whether this is what Sapkowski had in mind or not, the similarity in words is darkly fitting.