Theory

Greek theoria — looking at, contemplation, speculation. From theoros — spectator. Related to theater — both involve looking. Originally meant careful observation and contemplation before acquiring its scientific and philosophical meanings.

'It's just a theory' exploits the gap between the scientific and everyday meanings. In science, a theory is an explanation supported by extensive evidence — evolution, gravity, germ theory. In common use, theory means a guess. The gap is exploited systematically to undermine scientific consensus.