Why If you hang a dipole from one central support, typically a single mast or tree, the feedpoint sits at the apex and both legs slope down toward lower end supports, forming the shape of an upside down V. This is called an inverted V. Because the legs droop, the antenna behaves like a dipole with a slightly lower feedpoint impedance (often near 50 ohms) and a somewhat broader, less directional pattern than a flat-top dipole, and the ends can be much closer to the ground.
Watch out A sloper also uses one support, but it is a single slanted radiator run down from the top of a tower, not two legs drooping from a center feedpoint; an inverted L is an end-fed vertical section with a horizontal top wire, and a lazy H is a stacked pair of driven elements needing a wider supporting structure.
Picture the wire: center up, ends down, the letter V turned upside down. One support in the middle equals inverted V.