Ending –거든(요): it’s because, you see

거든() can be translated as “it’s because, you see.” It follows a verb and, in this form, is always ending a sentence (another pattern exists with 거든 in the middle of a sentence, with a different meaning). It is commonly used to add information to what was previously said, provide justification for one’s actions, or referring to something that was said in the past.

A: 왜 늦게 왔어?
B: 할 숙제 많았거든.
A: Why did you arrive late?

B: Because I had a lot of homework left.
프랑스에 가려고 해요. 프랑스어를 배우고 싶거든요. I will go to France. I want to learn French, you see.
한식말고 양식 먹을까? 매운 음식 되게 싫거든. Can we have Western food instead of Korean food? I really don’t like spicy food, you see.

Reference: Yeon, J., & Brown, L. (2011). Korean: A Comprehensive Grammar: Routledge.