From head +‎ board.

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headboard (plural headboards)

1. A vertical panel, either plain or upholstered, attached to the head of a bed.
2. (nautical) A panel, usually of metal, attached to the head of a fore-and-aft sail for additional strength.
3. (rail transport) A board on the front of a train, carrying the train's name or that of the service it is on.
   • 1939 June, “What the Railways are Doing: Novel Use of an Observation Car”, in Railway Magazine, page 462:

     A new use has been found for the L.M.S.R. observation car which previously worked in the Llandudno area. Mr. W. G. S. Wike writes that, still carrying headboards with the inscription "Llandudno and Blaenau Festiniog", it found its way to the Blackpool District, where it was used for familiarising enginemen with the various routes of access to this populous resort.

4. A grave marker made of wood.

• footboard
• bedhead
• bedboard
• headstone

• “headboard”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.

• Broadhead, broadhead