95% sureThese words were traced back to where they first appeared. That source is listed below.
What turned up
Letter to Andrew Crosse, Englische Studien Vol. 19 (1894), p. 157 ('Byron's Daughter' article) — full sentence: 'I mean to do what I mean to do,' closing a passage about her family's willpower. Fetched and confirmed verbatim.
Work
Letter to Andrew Crosse, printed in Englische Studien Vol. 19 (1894)
Occasion
circa 1844 · Ashley Combe, Somersetshire
Sources checked
ia801408.us.archive.orgChecked using claude-sonnet-5, 21 August 2026full OCR text, p.157, letter beginning 'My Dear Mr Crosse'
Nothing made from these words yet — is where they get made.