This term for 2 dissimilar organisms living together in mutualism comes from the Greek for "with" & "life"
[DOC] [TLE] Symbiosis | Define Symbiosis at Dictionary.com [PAR] Symbiosis definition, the living together of two dissimilar organisms, as in ... 1615
-25; < Greek symbsis, equivalent to sym- sym- + bi (variant stem of bion to 
live) + ...