The fact that he uses the word Nazgûl [~““35:51] from the Irish (nasc) and Scots Gaelic (nasg) words meaning “ring” to take a linguistic dig at Irish is notable. He was probably motivated by his political views of the time rather than celebrating (as one should) the value and diversity of all languages.
Tolkien once termed Welsh ‘the elder language of the men of Britain’; this talk explores how the sounds and grammar of Welsh captured Tolkien’s imagination and are reflected in Sindarin, one of the two major Elvish languages which he created.
Via https://podcasts.ox.ac.uk/medieval-welsh. For those interested on Tolkien, they’ve got a huge list of other scholarly content on his work: https://podcasts.ox.ac.uk/keywords/tolkien.