In the last few years I’ve heard those terms said in mountain biking than any other sport or activity. My first encounter with them would be during some downhill races that our team participated it. If I recall correctly, Tony Finch says it all the time.
Now that you’ve been enlightened with new vocabulary terms, let me shed some light on the proper usage.
Pin it: This can be used when someone is going through a turn or berm. Pinning something to a wall means that item you just pinned sticks. When it’s used in riding, you’re telling the person to stick to the trail. Below is great example of Corey Pond “pinning it” on a berm.
Now that you’ve learned the two important terms above, start using it. Impress your friends with your new found knowledge. Besides when you say it out loud during a group ride, your friends will think your cool.