Logan Rock is so-called because it 'logs' or 'rocks', or at least it did until Lieutenant Goldsmith pushed it off and had to pay to reset it. The name 'Treryn Dinas' comes from the Cornish for 'Fortress' (Dinas) [of a] 'Settlement' (Tre) [on] a point of land (rynn). 'Treen' is a shortened form of this also used for the nearby village.