§ Cris-caron ’Red Pass’ >> Criscarn (RS:419,433)
§ Cris-caron, Cris-carron, Cris Caron (RS:433)
These are names of the ’Red Pass’, a passage where the Misty Mountains may be crossed (in The Lord of the Rings just ’the pass of Caradhras’).
All names apparently contain N. criss ’cleft, cut’ (KIRIS-)
The adjective ’red’ takes again various forms; #carn appears as in Rathcarn. The form caron seems unusual, however. A parallel primitive form *carāna with a long ā could have produced caron by regular Noldorin change (compare NÁRAK- > narāka ’rushing, rapid, violent’ > N. narog). On the other hand final -on occurs several times in Ilkorin and three out of four examples are adjectives:
In his article on Ilkorin  Helge Fauskanger suggests a development via a final syllabic nasal -n:
This seems plausible and one may imagine *carn > *caron as a form parallel to #carn (perhaps more modern). In any case both -n and –on were already quite usual adjectival endings in Goldogrin often used both after final -r, as for instance barn, baron ’tilled, inhabited’ (GL:21); farn, faron ’separate, different, strange’ (GL:34); marn, maron ’ripe’ (GL:56). See also the note 4.4 at the end.
But a peculiar form is carron with double -rr- medially. It might be a result of assimilation of the combination -rn- as being syncopated *caran- > *carn- > *carr- with the same adjectival ending -on (< -ānā?). However, there are no similar examples, -rn- being a permitted cluster in Noldorin (and Ilkorin).
Assuming that the stem KARÁN- may be an extension of shorter *KAR- (although this clashes with KAR- ’make, do’), carron could be the result of two adjectival endings -rā and -nā with *-rānā > *-rauna > -ron. Compare WJ:392, where Tolkien discusses KWENE (whence Quendi ’speakers’) and KWETE ’speak, utter words, say’ as elaborations of KWE; and KWATA (whence Q. quat- ’fill’), KWAN as elaborations of KWA denoting ’completion’.