Holly Jolly

Most Christmas songs are stupid, but there’s one stupider than all the rest: Have A Holly Jolly Christmas.
I know what jolly means, but what the hell does holly mean?
Yes, I know it’s a plant. But in the context of the song, holly is meant to act as an adjective. Or as an adverb that modifies jolly.
When I last checked the dictionary, the only definition for holly is as a noun.
Can you have a holly jolly anything else?
Easter?
Birthday?
Blowjob?
Root canal?
No?
Then fuck you and your holly jolly Christmas.
I’m too busy celebrating Kwanzaa.