In Latin, camara or camera denoted a vaulted ceiling or roof. Later, the word simply mean “room, chamber” and was inherited by many European languages with that meaning. In the Spanish, the word became cámara, and a derivative of that was camarada “a group of soldiers quartered in a room” and hence “fellow soldier, companion.” That Spanish word was borrowed into French as camarade and then into Elizabethan English as both camerade and comerade.