Green’s Dictionary of Slang

a rich, hedonistic, stupid young woman, due to inherit a large fortune; occas. of a man.

1986		People (US) 13 Oct. 🌐 Sarah has already resumed her publishing job (Di couldn’t have a career if she wanted to), proving to her public that she is not only fun but a lot more than a royal heirhead with an ever-so-slightly risque past.
2003		Palm Beach Post 2 Dec. 🌐 Dancing on tables at wild parties. Catfighting in a club over some guy. Taping yourself having sex -- and then taking a cellphone call in the middle of the shenanigans! No wonder they’re calling Paris Hilton an ‘heirhead.’.