Purely means only and entirely for that reason. Purely by chance, purely academic, purely and simply.
It narrows rather than intensifies — purely coincidental says nothing else was involved, not that the coincidence was strong. Purely academic means having no practical effect, which is a slight against academics buried in ordinary speech.
1adverbpurelyOnly and entirely for that reason.
“She took the job purely for the money.”
purely is a limiting.
Pure plus -ly, from Latin purus, clean or unmixed. The word keeps the sense of nothing else mixed in.
Middle English
purely
English, today
purely
From Middle English purely, equivalent to pure + -ly.
Etymology from Wiktionary, CC BY-SA