fons et origo

I seem to understand that this gentleman […] is the fons et origo of the trouble; and, from what I gather, he has already paid through the nose.

1889, Robert Louis Stevenson, Lloyd Osbourne, “Final Adjustment of the Leather Business”, in The Wrong Box, London: Longmans, Green, and Co., →OCLC, page 282

Mention of other Congressmen in the same connection is by the way. I seem to be the fons et origo of all the evil imputed to the Congress. If I have not ceased to be your friend, why did you not, before taking drastic action, send for me, tell me of your suspicions and make yourself sure of your facts?

1942 December 31, Mahatma Gandhi, “Letter on New Year’s Eve: May the New Year bring peace to us [Letter to Lord Linlithgow]”, in R. L. Khipple, editor, Famous Letters of Mahatma Gandhi, Lahore: The Indian Printing Works, published 1947, page 132

As dramatic cures were occasionally seen in rheumatoid arthritis after overwhelming near-fatal disease, and as a school of thought favoured the central nervous system as the fons et origo of rheumatoid arthritis, ECT and insulin coma were both tried.

1976 March 27, F. Dudley Hart, “History of the treatment of rheumatoid arthritis”, in British Medical Journal, volume 1, number 6012, →DOI, →JSTOR, page 764