perhaps from ops, "sight," denotes "a hole, an opening," such as a fissure in a rock, Heb 11:38. In Jam 3:11, the RV has "opening," of the orifice of a fountain (AV, "place"). See PLACE.
<2,,4693, spelaion>
"a grotto, cavern, den" (Lat., spelunca), "cave," Joh 11:38, is said of the grave of Lazarus; in the RV in Heb 11:38, Rev 6:15 (AV, "dens"); in the Lord's rebuke concerning the defilement of the Temple, Mat 21:13, Mar 11:17, Luk 19:46, "den" is used.