One is basically a spelling pronunciation of the English form of the
name. The other is the Gaelic Cnòideart. You get the same kind of
variation in Ireland. The Gaelic word for hill is "cnoc", which in
place-names often becomes "Knock" in English and thus is pronounced
"Nock". In some dialects of Gaelic an initial [kn] becomes [kr], and
therefore many place-names begin with Crock in English.
The "d" in the second syllable is palatal in Gaelic. This doesn't come
across in the anglicized version. This reminds me of the village of
Gortin in Tyrone, where the "t" is palatal in Gaelic, "Goirtín" (the "i"
before the "t" is there as an advance warning of that, like the "i" in
Cnòideart), and locals pronounce it Gorchin.
I confess I don't know why the "t" at the end of Cnòideart is pronounced
[st].
--
James