Walz is from Minnesota. Minnesota is in the Midwest. Some people in the Midwest have a unique and rather quaint dialect and accent, as well as a very friendly culture.

“'Ope” is an exclamation akin to “Oops”, and is often said when a Midwesterner may have accidentally bothered someone in some way (e.g. bumping into them accidentally).

This exlamation is often followed up by “sorry boutcha” to form the iconic phrase: “Ope! Sorry boutcha!” Which is basically the folksy, Midwestern equivalent of “I beg your pardon”.

Ope has beocme an iconic, memetic symbol of Midwestern identity, culture, and stereotypical friendliness.