From kaphaph; a hollow rock -- rock.
see HEBREW kaphaph
H3710. keph
[כֵּף] noun [masculine] rock (Assyrian kâpu DlHWB 346; Aramaic כֵּיפָא, perhaps Aramaic loan-word in Hebrew; √ dubious); — only plural כֵּפִים Jeremiah 4:29 as place of refuge; Job 30:6 as dwelling-place.