gap (n.) Look up gap at Dictionary.com
early 14c. (mid-13c. in place names), from Old Norse gap "chasm," related to gapa "to gape," from PIE *ghai- "to yawn, gape" (see yawn (v.)). Originally "hole in a wall or hedge;" broader sense is 16c. In U.S., common in place names in reference to a break or pass in a long mountain chain (especially one that water flows through). As a verb from 1847.