I first encountered this word during my first year in law school. It came out in the finals exam in Legal Profession. I didn't encounter the word before then, I haven't encountered the word again after that. But it always seems to pop in my mind, like LSS. What's irritating is that I do not know its definition (also like LSS, when you don't know the lyrics). So I looked it up, for my own peace of mind.
This funny sounding word is defined as an unethical agreement between an attorney and client that the attorney would sue and pay the costs of the client's suit in return for a portion of the damages awarded.
Trivia: in the history of Philippine jurisprudence (according to me), the term champerty has been used only once, in Hernandez v. Villanueva (way back in 1920).