As nouns the difference between ranny and cranny
is that
ranny is (obsolete|outside|dialects) a shrew (in the sense of the mouselike animal) while
cranny is a small, narrow opening, fissure, crevice, or chink, as in a wall, or other substance.
As a verb cranny is
to break into, or become full of, crannies.
As an adjective cranny is
(uk|dialect) quick; giddy; thoughtless.