Second-wave was a term used by the original settlers of the planet Jelucan to describe the settlers that arrived 350 years after the initial settlement of the planet.
The second-wavers were a group that had settled on the planet Jelucan largely comprised of wealthy aristocrats. They held most of the authority over the planet until the arrival of the Galactic Empire. The second-wavers considered the First Wavers, the original settlers of the planet to be filthy and backwards. In turn, the original settlers believed the second-wavers were disloyal and greedy.
Approximately 500 years before the planet Jelucan's annexation under the Galactic Empire, a small group of settlers arrived on the planet in an attempt to escape an oppressive king. 350 years later a second-wave of settlers arrived on the planet, in hopes of establishing mining operations on the planet. These 'second-wavers' prospered, leaving the original settlers to wallow in poverty. The disparity in wealth caused a division between the two groups, which in turn led to a degree of prejudice between them.
Dalven Kyrell, the older brother of Thane Kyrell, disapproved of his brother's friendship with a First Wave girl named Ciena Ree. Dalven told Thane that there was "only one reason" to associate with a girl from the valleys (where the First Wavers lived)—and if that was what Thane was after, he ought to get one who had breasts already. That rude comment led the younger Kyrell to attack his brother for the insult to his friend.