여야 되다

it has to be that thing

This attaches to a noun and says the thing has to be that and nothing else: it has to be a word, it has to be a different one, it has to be off the beat, it has to be dialect, does it have to be a completely absurd state. Several of these lines are people working out the rules of a game, which is exactly where this phrasing turns up most. For verbs the equivalent form is the ordinary have-to ending.

Register: casual; often rule-clarifying