quejarse
/keˈxaɾse/ · B1 · verb
to complain, to whine, to gripe, to grouse, to fuss, to bitch, to beef
📢 From Latin quassare, to shake or shatter, the same root as English quash
Quejarse comes from Vulgar Latin quassiare, from quassare 'to shake, to break'. English quash comes from the same root. Una queja is a complaint. It's reflexive, so the -se goes with the person: me quejo, te quejas, se queja de todo.