Map of the Marilyns of Britain and Ireland

From the Scotland/Wales-dominant distribution, and the absence of Marilyns in London, one might surmise that the term as used here does not refer to people.

A "Marilyn" is a mountain or hill with a relative height (elevation above its surroundings) of at least 150 meters. The term was coined as a pun on the comparable term "Munro," which refers to a Scottish mountain over 3000 feet high. Ben Nevis and Snowdon are Marilyns, as are some sea stacks.

Curiously, probably based on its etymology, the term Marilyn appears to retain its capitalization; one would think that having been "genericized" it would revert to lower case.