Good question, Sinistar!
In a nutshell, I haven't been able to find an authoritative source on
whose idea it was or precisely when the practice began, but all signs
point toward the tradition having begun with the Picholine olive
sometime during the 18th century in the Provence region of France.
Apparently, you're not the only one asking this question. Here's a
link to an "Ask Yahoo" question, including some interesting
speculation on the topic:
From this page, "All freshly picked olives, no matter how ripe, have a
vile, intensely bitter taste. In order to make them palatable, they
must be pickled. Since pimentos are sweet and indigenous to the
Mediterranean, it's easy to imagine an innovative farmer or chef way
back when thinking they would make the perfect neutralizer to the
olive's natural acidity"
This page provides a wealth of detail on olives and their great
"The broad-leaved olive trees of Spain bear a larger fruit, but the
pericarp is of more bitter flavor and the oil of ranker quality. It is
these Spanish olives that are usually cured and eaten, often after
being pitted, stuffed (with pickled pimento, onion, or other
garnishes) and jarred in fresh brine."
This page contains a catalog entry for the Picholine olive, which they
claim were the olives that were first stuffed, and dates the origins
of olive stuffing 'as early as the 18th century':
<...>As early as the 18th century, producers of Picholine olives in
Aix-en-Provence were stoning their olives and replacing the stone with
capers, anchovies, tuna, and pimiento. This was the beginning of the
tradition of stuffing olives, a popular practice still today.<...>"
This page provides a discussion of olives from the book "History of
Druggs" by Monfieur Pomet, published in 1709:
From this page:
"For the Spanish Olives they are as big as a Pigeon's Egg, of a pale
green, and bitter Taste, which does not please every Body; but for the
Provence, especially the Picholine Olives, they are reckon'd the best,
because it is pretended that Messieurs Picholini of St. Chemes knew
how to pickle them better than other People, since those are the
finest and best Olives, because they are much greener, and of a better
Taste than the Pauline and other Olives of Provence. They are of
delicate Nutriment, stomachick, pectoral, antiscorbutick, gently
loosen the Belly, and are chiefly us'd as Sallading."
Notable here is the fact that the pickling recipes are fairly
detailed, but no mention is made of stuffing olives. So, it seems
likely that the tradition, if begun at all by this time, was not yet
widespread enough to appear on the radar.
As this passage refers specifically to the Picholine variety, it is
almost safe to say that the practice began sometime after the
publication of this book.
Another factor that may be significant in pinning down a date is on
this page, in an article by the legendary James Beard:
"Contrary to certain confusing etymological implications, the large,
red, heart-shaped pimento pepper (indigenous to the Americas and taken
back to Spain by Columbus)"
If this is true, then at the very least, the practice could not have
begun until well after Columbus returned to Spain, and the pimento had
had a chance to take hold in the region. This is a very broad range,
of course, but it does indicate that pimentos didn't exist in Spain or
France until the mid-13th century, and wouldn't have been widely
available in the region until some time later.
Based on this information, the practice of stuffing olives with
pimento definitely didn't occur prior to Columbus returning to Spain,
and probably didn't occur until sometime during the 18th century, as
indicated by Monfieur Pomet's lack of information on the topic.
Here's some more background on pimentos, if you're interested:
And here is a brief page describing the history of olives (no mention
of the history of stuffing olives, unfortunately):
Thanks for such an interesting question, and don't hesitate to ask if
you'd like further clarification.
olives pimentos history
olives pimientos history
"stuffing olives" practice