John Gambrill Nicholson (the Francis was added later and the -ll/-l spelling varied over the years) was born at Saffron Walden, Essex, the son of an ironmonger's assistant. He was educated locally at the King Edward VI Grammar School before entering upon his career (without any formal qualification) as an English Master at various schools in England and Wales: Buxton (1884–7); Ashton (1887–8); Rydal Mount School, Colwyn Bay (1888–94), where he also coached the football team; Arnold House School, Chester (1894–6); Stationers' School, Hornsey, north London (1896–1925, retired).
His first book of poems Love in Earnest (1892) was dedicated to the memory of his mother, but the first section, a sequence of 50 numbered sonnets (which open with "Some lightly love, but mine is Love in Earnest -/My heart is ever faithful while it hears/An echo of itself in thine, though years/Should pass ere its full passion thou returnest"), was dedicated to "W.E.M." This was the flaxen-haired blue-eyed William Ernest Mather (1877–99)—second son of Sir William Mather—a pupil of his at Rydal Mount School 1888–90, who died young after being thrown from his horse. A photograph of Nicholson with Ernest, taken at Llandudno in June 1889, was published in The Book Collector (Summer 1978). The dedicatees of other individual poems, referred to only by their initials, can be identified in many cases from the school register.
