The only free and comprehensive online etymological dictionary of the Spanish language
cama f. (Noun) "bed"
13th cent. From a pre-Roman language, usually assumed to be Iberian but ultimately unknown. Also the origin of the surname Cama, first given to bed-makers and sellers.
Indo-European
Romance
Asturian cama, Leonese cama, Portuguese cama, Galician cama

The word originally indicated a straw bed while lecho was the generic term for bed. Cama eventually replaced lecho in the medieval period.