Her father John Gwynn was a Syriacist and Regius Professor of Divinity at Trinity College Dublin.

Her role as women's registrar was described by one of her charges as "to control our movements to some extent and to protect the college and the students from criticism".

[6] In 1907 Lucy Gwynn was summoned before the Fry Commission on Dublin University to defend the position of women at Trinity.

From her mother's brother Robert Donough O'Brien (1844-1917), an architect, she inherited the house he had designed and built at Parteen-a-Lax in County Clare, close to Limerick City.

[9] Founded, by subscription, in 1948 in memory of Lucy Gwynn it is awarded annually in the Michaelmas term to a Junior Sophister woman student for distinction in her course.