Some background for the unfamiliar:

“OP” is the abbreviation for “Ordo Prædicatorum”, or “Order of Preachers” in English, aka the Dominicans.

Saint Dominic is the founder of their order.

that’s a ridiculous way to remember it when you can easily tell it’s the number you would get if you concatenate the single digit even numbers excluding 0 in ascending order and divide it by 2.

That’s the kind of combination an idiot would have on his luggage