A buckle connect one end of something to the other.

Verb buckle means to attach or fasten.

But what could this mean?

Buckle down, Jonathan.

Are you coming to the office party after work today?

I wish I could, but I need to buckle down and practice for my show this weekend.

I don't know any of the songs yet.

Wow.

Yeah, you had better buckle down.

Yeah.

Wish me luck.

To buckle down means to get serious about a task for problem.

When you buckle down, you commit yourself toe working part in our example, Jonathan says he needs to buckle down and learn the songs for his upcoming show, and that's English in a minute.