what was the name for black sabbath before the became black sabbath ?

because years ago was watching vh-1 behind the music of black sabbath which they are my all time favorite i would considered them the first heavy metal band over led zepplin any day but what i am getting at they said on their they were called earth and and seen them performing elvis song blue sade shoes which they sounded awsome i was just wondering isf thats true they were called earth ?

thanks for the insight more on your answer i was half right on them being called earth but i never knew they were called polka tulk