ˈaɪm ə ɡəˈnuː …
ju ˈrɪəli ˈɔːt tə kəˈnəʊ wəˈhuːz wəˈhuː
əʊ ɡəˈnəʊ ɡəˈnəʊ ɡəˈnəʊ, ˈaɪm ə ɡəˈnuː
We know that really in words spelt gn- the g is silent (= there is no associated sound g): gnaw, gnarled, gnat, gnash, gnome. So I suppose we really should be saying nuː, or possibly njuː. But in serious discourse this animal is usually called a wildebeest (which we can debate whether to pronounce with w or with v). In even more serious discourse we can use its scientific name, Connochaetes (though the OED for some reason thinks it is Catoblepas).
The etymology of gnu is given in the OED as “Hottentot word”. But in the Concise Oxford this is replaced by the slightly more precise “Bushman nqu, probably via Dutch gnoe”. Neither “Hottentot” nor “Bushman” is the name of a language in polite circles these days: the first we call Khoe, Khoekhoe or Nama, while the second term refers to any of a number of languages, including !Kung (!Xũũ) and !Xóõ. I wonder from which of the Khoisan languages, then, the word derives.
_ _ _
The sports reporter on the Today programme (BBC R4) this morning was having trouble with the name of a racehorse, Abriachan. This came up at 06:25 and was followed by a brief impromptu studio discussion of what might be the correct pronunciation. An hour later, it was time to repeat the report, and I’m glad to say that by then the producer had tracked down the trainer of the racehorse, who was able to tell us all over the phone that it was named after a village in the Scottish Highlands, pronounced əˈbriːəxən.
They could just have consulted Wikipedia.