different between gunwale vs oarlock

English

From Middle English gonnewalle, itself from gonne (“gun”) + wale, as it used to support the ship's guns; equivalent to gun +? wale.

gunwale (plural gunwales)

(nautical) The top edge of the hull of a nautical vessel, where it meets the deck.

Webster's Seventh New Collegiate Dictionary, Springfield, Massachusetts, G.&C. Merriam Co., 1967

oar +? lock

oarlock (plural oarlocks)

A device attached to the gunwale of a rowboat to hold the oars in place while rowing.
- 1906: Horatio Alger, Joe the Hotel Boy [1]
  But, as luck would have it, scarcely had he started to row his boat again when an oarlock broke, and so it took him the best part of an hour to make the trip.