It means to get married or commit to a monogamous relationship; probably the two most indicative words for the situation itself, born of a word that can mean "to move downward; sink, or descend," "to subdue," and "to conclude," and a word that means the "opposite of up."

used in heated situations

verb. seh-tul down - 1) to stop knocking some one's fork on the floor especially at a cracker barrel. 2) to stop laughing uncontrollably to the point of endangering people within the area.