Word Origin of Tailgate

–noun

1.	the board or gate at the back of a wagon, truck, station wagon, etc., which can be removed or let down for convenience in loading or unloading.

–verb (used without object)

2.	to follow or drive hazardously close to the rear of another vehicle.

–verb (used with object)

3.	to follow or drive hazardously close to the rear of (another vehicle).

–adjective

4.	pertaining to or set up on a tailgate: a tailgate picnic before the football game.

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Origin:
1850–55, Americanism; tail ¹ + gate