Hops are what give beer the Citrusy, Piney, or sometimes what bring out the Herbal or Fruity flavors.
Decades later, beer aficionados appropriated the term to refer to themselves (with a wry tip of the hat to it's original meaning).
<Beer Drinker #2> You, sir, are a hophead.
Willie the Weeper, yeah, the chimney sweeper
He had the hop-habit and he had it bad
Lemme tell you 'bout a dream he had"
--old ragtime song about opium.
IPAs (India Pale Ale) or Double IPAs are examples of beer styles that are favored by hopheads.
Dad: "I want all those damned hop heads off the place, NOW!"