The specific name, illingworthorum, which is genitive plural, is in honor of Margaret and Percy Illingworth.

[3] A large, rock-dwelling gecko from the dry zone of Sri Lanka, C. illingworthorum is distributed in the monsoon forests of the eastern parts of the country, such as Namadagala, Monaragala, Nilgala, Gal Oya National Park, Buttala, and Ampara.

[citation needed] C. illingworthorum inhabits rocky biotopes, such as granitic caves within savannah and monsoon forests.

Its diet comprises large insects, such as dipterans, coleopterans, their larvae, glow-worms, and other arthropods.

[2] Eggs, measuring 14.9 by 8.2 millimetres (0.59 in × 0.32 in), are produced at communal nesting sites, glued to rock surfaces.