This is an old list of a living things that Ents learned when they were young. Treebeard recited this when he met Merry and Pippin, trying to figure out where hobbits were in the list. When he bid goodbye to them at the fall of Isengard, he had added them in.

Learn now the lore of Living Creatures!
First name the four, the free peoples:

Elders of all, the elf-children;
Dwarf the delver, dark are his houses;
Ents the earthborn, old as mountains;
Man the mortal, master of horses:

Beaver the builder, buck the leaper,
Bear bee-hunter, boar the fighter;
Hound is hungry, hare is fearful…

Eagle in eyrie, ox in pasture,
Hart horn-crowned; hawk is swiftest,
Swan the whitest, serpent coldest…

Ents the earthborn, old as mountains,
The wide-walkers, water drinking;
And hungry as hunters, the Hobbit children,
The laughing-folk, the little people.

~The Two Towers, “Treebeard”

Merry: It’s been going for hours.
Pippin: They must have decided something by now.
Treebeard: Decided? No, we have just finished saying “Good Morning”.
Merry: But it’s night time already! You can’t take forever!
Treebeard: Now, don’t be hasty, master Merriadoc.
Merry: We’re running out of time!

Treebeard: You must understand, young Hobbit, it takes a long time to say anything in Old Entish. And we never say anything unless it is worth taking a long time to say.

Treebeard: I promised Gandalf I would keep you safe and safe is where I’ll keep you.

Treebeard: That doesn’t make sense to me. But, then again, you are very small.
Pippin: And whose side are you on?
Treebeard: Side? I am on nobody’s side, because nobody is on my side, little orc.

Treebeard: I always like going South; somehow, it feels like going downhill.

Treebeard: I believe you will enjoy this next one, too. It is one of my own compositions. Ahem. ‘Beneath the roof of sleeping… leaves and dreams of trees untold, When woodland halls are… green… and cool, and the wind is in the west, Come back to me… Come… back… to me, And say my land is… best.’

Pippin: Why are there so few of you, when you live so long? Are there Ent children?
Treebeard: [Sadly] Brrharroom. There have been no Entings for a terrible long count of years.
Merry: Why is that?
Treebeard: We lost the Entwives.
Pippin: Oh, I’m sorry. How did they die?
Treebeard: Die? No. We “lost” them. And now, we cannot “find” them.
Treebeard: [hopefully] I don’t suppose you’ve seen Entwives in the Shire?
Merry: Can’t say that I have. You, Pip?
Pippin: [thinks for a moment] What do they look like?
Treebeard: [pauses] Hrrooom… I… don’t… remember… now.

Ents’ Marching Song

We come, we come with roll of drum: ta-runda runda runda rom!
We come, we come with horn and drum: ta-runa runa runa rom!

To Isengard! Though Isengard be ringed and barred with doors of stone;
Though Isengard be strong and hard, as cold as stone and bare as bone,
We go, we go, we go to war, to hew the stone and break the door;
For bole and bough are burning now, the furnace roars – we go to war!
To land of gloom with tramp of doom, with roll of drum, we come, we come;
To Isengard with doom we come!
With doom we come, with doom we come!

~The Two Towers, “Treebeard”.
Sung by the Ents as they marched south to make war on Saruman and destroy Isengard.