Singularly means to a remarkable and unusual degree. Singularly unhelpful, singularly beautiful, singularly ill-suited.
It is formal and it very often modifies something negative — singularly unhelpful, singularly inept — where the word adds a note of dry disapproval. It means uniquely rather than merely very. Note singular, both the grammatical term and the adjective meaning remarkable.
1adverbsingularlyTo a remarkable and unusual degree.
“It was a singularly beautiful evening, with the sky turning pink over the sea.”
singularly is a degree of remarkableness.
Singular plus -ly, from Latin singularis, alone of its kind, from singulus, one each. Single comes from the same one.
Middle English
singulerly
English, today
singularly
From Middle English singulerly; equivalent to singular + ly.
Etymology from Wiktionary, CC BY-SA