As a noun gulley
is (etymology 1).
As a proper noun cliff is
a diminutive of the male given name clifford .
cliff
Etymology 1
(etyl) clif .
Noun
(
en noun)
A vertical (or nearly vertical) rock face.
Synonyms
* precipice
Derived terms
* cliff swallow
* cliff-face
* cliffed
* cliffhanger
* cliffing
* cliffy
Etymology 2