The original term for the computer was actually attributed to people who would crunch numbers and convert them by hand, on paper, using a pen or a pencil and other 'modern' gadgets at the time. They were literally the computers.
Human computers at work. What are they using?
Source
They worked in all manner of professions, including finance and engineering. Computers as we know them were introduced in the 1970's, thereby replacing the whole profession.
Another interesting profession that has fallen off the cliff historically is that of a daguerrotypist. These are the people who created images on silvered copper plates for their distinguished clientele between 1839 and 1860.
They did this using a technique that imprinted a lifelike image on a fragile plate of mirror-like surfaced metal that had to be presented within a protective casing.
(YouTube)
Other techniques were later invented that were much cheaper and accessible to the masses that rendered this approach obsolete.
Sources:
https://www.historydefined.net/professions-that-no-longer-exist/
https://www.businessinsider.com/weird-jobs-that-no-longer-exist-2014-9#groom-of-the-stool-16
