the.com/lookalike

means A person or thing that closely resembles another, especially a stranger who could pass for someone else's double.

from A straightforward 20th-century compound of 'look' plus 'alike' — no hidden trickery here, it does exactly what it says. It emerged as English got increasingly fond of smashing two plain words together to name a new idea (think 'soundalike' following the same pattern), rising alongside celebrity culture and photography, when the idea of someone sharing your exact face became something worth naming.