Come UpTo come up is to appear, sometimes unexpectedly or suddenly, in a series of events or on an occasion, to arise in a discussion.
EX: When preparing to blast into space, the astronauts never thought a fuel leak would come up during the flight, leaving them unprepared for what lay ahead.
EX: His boss, increasingly frustrated with the errors that would only come up on the days his new employee manned the cash register, fired him.
To come up through the ranks is an expression that means to work one's way up a hierarchical ladder from a low position to a high one. Someone who has put in a significant amount of time or effort into an organization to achieve a position could be said to have come up through the ranks.
EX: John, knowing full well that he would have to come up through the ranks to become successful, was thus satisfied with the low position he was initially assigned.
EX: The private knew he would have to come up through the ranks to have any chance of promotion, but he had no idea of the toll that war takes on an individual.
Come OutWhen something is said to come out, it means that it is discovered or found out about, as in a secret or a new fashion item coming out.
EX: Jody had been able to keep the secret about his high school glee club membership and he hoped the story would not come out.
EX: When the newest boots for the fall came out, Sheila realized the pair she had bought at the end of last season were hopelessly out of style.
To come out is also an expression often use to describe a person's decision to reveal that he or she is a homosexual, or to come out as gay or lesbian.
EX: Before he made the decision to come out, John had weighed up the question of whether or not he believed it was a good time to do so.
EX: For many people who come out to friends and relatives, the experience can be a relieving and positive one.