Gwyneth Lewis chose Emily Dickinson for this week’s Great Lives on Radio 4.
The word recluse was chosen to describe her.
You certainly couldn’t call her a loner, though these days I suspect that most recluses would be called loners, at least by those who wished to imply there was something dangerously odd about them - though of course Seneca too condemned the evil of departing from the company of the living before you die
The OED finds written instances of the word loner dating back to only 1947 in America, & even has a quote from Guardian in 1961 which seems to attribute the coinage to James Jones.
