The phrase comes from French slang, where tema means look or check out, and it spread online as a repeatable reaction line in French speaking meme communities. Short clips pairing the shout with rats, oversized animals and distorted wide angle shots helped it travel beyond its original context, and the line is now quoted even when no rat is present. Its appeal is the instant exaggeration, so creators reuse it as shorthand for stunned disbelief at any size reveal.