Definition of "shellacked"

At Boy Bar, the bouncers, two tall, emaciated young men with shellacked hair under their bowler hats, were standing just inside the door to escape the cold.

1986, David Leavitt, The Lost Language of Cranes, paperback edition, Penguin, page 41

Those were my first impressions of wine: Ladies drink chilled, soft white while they gossip in the kitchen; old men drink strong, room-temperature red to get shellacked.

2014, Maximillian Potter, Shadows in the Vineyard