Perhaps Conan was drunk, and called the woman that by mistake! Perhaps he used the word as slang for 'woman' which is rarely used nowadays. There is a song by Led Zepplin from the 1970s with these lyrics: "Hey, hey momma said the way you move, gonna make you sweat, gonna make you groove." That is "momma" as slang for woman, too. :) Considering the context of the Conan movie, he may have called the woman "mama" because she was much older than him. "Woman old enough to be my mother" = "mama" slang

A lot of American guys call older women Mom. My son's friends call me Mom. It's just an endearing term.

Mom and mama mean the same. Like when a small baby cries mama and doesn't know what it is saying.