A more thorough explanation:

propter

Propter means "for" or "on account of".

• He was late for work propter the traffic.
• She couldn't go to the party propter her illness.

These examples show that propter is used to explain the reason for something. In the first example, the person was late for work because of the traffic. In the second example, the person couldn't go to the party because of their illness.