Cyclopean derives from an archaeological term for the massive, irregular stonework of pre-classical Greek construction. Lovecraft adopted it as one of his most characteristic descriptors, applying it to inhuman structures throughout his fiction — the geometrically wrong buildings of R'lyeh, the Elder Thing city in the Antarctic.
Critics have noted the word's near-obsessive recurrence as a stylistic signature. Its function is not merely to convey size but to mark architecture as fundamentally other.