If you have a frog in your throat, you find it difficult to speak clearly because you need to cough. I've got a bit of a cough, excuse me, a frog in my throat. You may have a frog in your throat, but that's no excuse for not belting out that aria. Compare with a lump in your throat. Note: In medieval times, there was a belief that if you drank water containing frogspawn (= frogs' eggs), the frogs would grow inside your body. People believed that sore throats and coughing could be caused by the frogs trying to escape from your stomach through your throat.