From Wiktionary, the free dictionary
Initialism from the names Harry and Hermione.
H/H (uncountable)
- (fandom slang) The ship of characters Harry Potter and Hermione Granger of the Harry Potter series.
2001 December 28, CrimsonRiver, “From GOF, a H/H relationship set up”, in alt.fan.harry-potter[1] (Usenet):My daughter was finishing GOF & she was like, "Look! Here is the foreshadowing of the H/H relationship!"
2002 September 7, Tom, “Re: Poll: Ron with Hermione or Harry with Hermione?”, in alt.fan.harry-potter[2] (Usenet):Also I DON'T think like some H/H shippers that kiss on the cheek was a 'sign'.
2003 March 24, Meliss9900, “Re: Re: Hermione”, in alt.fan.harry-potter[3] (Usenet):IMO H/H have been built as being compatible over the series while R/Hr are shown as volatile.