Tannenbaum
This is German for “fir tree” (“tanne” + “baum”).
It’s not “Christmas tree” – that’s “Weihnachtsbaum,” but you’ll see below that it’s used in that context.
Why I Looked It Up
Over the holiday season, I heard the Christmas song “Oh Tannebaum” a couple of times. I got to wondering about it.
O Tannenbaum, O Tannenbaum,
How faithfully you blossom!
Through summer’s heat and winter’s chill
Your leaves are green and blooming still
Note that in some English translations, “Tannenbaum” is also translated as “Christmas tree” (it has the same number of syllables).
Postscript
Added on
I had a conversation with a German friend about it:
Me: How do you say “Christmas tree” in German?
Them: we say Weihnachtsbaum
Me: Then what does “tannenbaum” mean?
Them: That’s the actual name of the tree itself. “Weihnacht” just means Christmas
Me: So, the song “Oh Tannebaum” isn’t saying “Oh Chrismas Tree”?
Them: Oh Tannenbaum is a Christmas song but Tannenbaum is the translation to fir tree I guess
Me: So it’s saying, “Oh fir tree, oh fir tree”?
Them: Yes exactly. German language is weird haha
Me: “Baum” is tree?
Them: yes. have you heard that song in the US?
Me: Yes. Sometimes it’s “Oh Tannebaum” and sometimes it’s “Oh Christmas Tree.” Like, in the first case, they translate everything into English except “Tannenbaum.” And when they do translate that, they translate it wrong, I guess. So the syllable count matches? And it makes sense. Because who sings a song about fir trees?
Them: ahh I see. yeah Christmas tree makes more sense in English as it’s a Christmas song