Cottesloe is a western suburb of Perth, Western Australia, within the Town of Cottesloe. Cottesloe was named for Thomas Fremantle, 1st Baron Cottesloe, a prominent Tory politician and the brother of Admiral Sir Charles Fremantle for whom the city of Fremantle was named. The nearby suburb of Swanbourne was named for the Fremantle family seat, Sw…Cottesloe is a western suburb of Perth, Western Australia, within the Town of Cottesloe. Cottesloe was named for Thomas Fremantle, 1st Baron Cottesloe, a prominent Tory politician and the brother of Admiral Sir Charles Fremantle for whom the city of Fremantle was named. The nearby suburb of Swanbourne was named for the Fremantle family seat, Swanbourne House, in Swanbourne, Buckinghamshire.