Al-ka, (letter); first letter of the Gorean alphabet; corresponds to the Earth letter 'A'. 

... a metal frame with rollers at the top and bottom and, pushing a button, spun the scroll to its opening mark, a single sign.
"Al-Ka!" said Torm, pointing one long, authoritative finger at the sign. "Al-Ka," he said.
"Al-Ka," I repeated. I had begun to learn the Gorean alphabet. 
Book 1, Tarnsman: pg 38

I nodded. The rest of it I did not need to be told. The expressions 'Al-Ka' and 'Ba-ta' are the first two letters of the Gorean Alphabet. In effect these men had no names, but were simply known as Slave A and B. 
Book 3, Priest-Kings: pg 94