Green’s Dictionary of Slang

Stroke City n.

[SE stroke, a solidus + -city sfx; the dual names of the city, claimed respectively by Catholics/Protestants and the futile attempt to rename it ‘Londonderry/Derry’]

(Ulster) Derry/Londonderry, Ireland.

[Ire]Eve. Herald (Dublin) 4 Jan. 30/5: [headline] Life and Times in Stroke City.
Irish Indep. (Dublin) 10 Jan. 9/4: He [i.e. Gerry Anderson] overcame the problem of how to describe the city to keep both sides of the community happy — it became Derry/Londonderry and later just ‘Stroke City’.
[UK]Guardian 30 Jan. [Internet] The name of the city on the banks of the River Foyle has always been a contentious issue. Most Protestants refer to it as Londonderry, while Catholics call it Derry. Local BBC radio presenter Gerry Anderson coined the diplomatic pseudonym ‘Stroke City’ after wrestling on-air with the unwieldy ‘Derry/Londonderry’.