Before 2007, asking David Grais and Kathryn Ellsworth about collateralized debt obligations and mortgage-backed securities would have probably resulted in a decent amount of head-scratching between the pair.

But for the founders of four-year-old Grais & Ellsworth, those toxic assets have come to give their firm a sense of purpose. The firm’s name graces complaints that companies including The Charles Schwab Corp. filed against Wall Street banks over billions of dollars in lost investments in mortgage-backed securities. Even the Federal Deposit Insurance Corp. is now a client.