"While it is a common mistake to regard the scimitar as a weapon exclusive to the Middle Eastern world, scimitars and straight swords existed side by side in the region for millennia. In the 7th century, scimitars first appeared among the Turko- Mongol nomads of Central Asia. A notable exception was the sickle- sword of ancient Egypt, which appeared to be an outgrowth of a battle axe rather than a true sword. As successive waves of nomads spread through Asia, their curved swords were adapted by the Indians, Persians, Arabs, and Chinese. With the steppe warriors migrating farther west, the scimitar entered Eastern Europe by way of Russia and Ukraine. The spread of the scimitar into Central and Western Europe can be tracked linguistically. From sabala of the Turkic-speaking peoples of Central Asia, it became sablya in the Russian language, szabla in Hungarian and Polish, sabel in German, sabre in French, and saber in English."
https://nationalinterest.org/blog/the-buzz/scimitar-how-one-sword-dominated-warfare-centuries-25033
"The name is thought to be derived from the Persian word shamshēr which literally means “paw claw,” due to its long, curved design. The word has been translated through many languages to end at scimitar. In the Early Middle Ages, the Turkic people of Central Asia came into contact with Middle Eastern civilizations through their shared Islamic faith. Turkic Ghilman mamelukes serving under the Umayyad and Abbasid Caliphates introduced "kilij" type sabers to all of the other Middle Eastern cultures. Previously, Arabs and Persians used straight-bladed swords such as the earlier types of the Arab saif, takoba and kaskara."
https://en.wikipedia.org/wiki/Scimitar
"The Central Asian Turks and their offshoots begun using curved cavalry swords beginning from the late Xiongnu period.[3] The earliest examples of curved, single edged Turkish swords can be found associated with the late Xiongnu and Kok Turk empires.[4] These swords were made of pattern welded high carbon crucible steel, generally with long slightly curved blades with one sharp edge. A sharp back edge on the distal third of the blade known as "yalman" or "yelman" was introduced during this period.
In the Early Middle Ages, the Turkic people of Central Asia came into contact with Middle Eastern civilizations through their shared Islamic faith. Turkic Ghilman slave-soldiers serving under the Umayyad and Abbasid Caliphates introduced "kilij" type sabers to all of the other Middle Eastern cultures. Previously, Arabs and Persians used straight-bladed swords such as the earlier types of the Arab saif, takouba and kaskara.
During Islamizaton of the Turks, the kilij became more and more popular in the İslamic armies. When the Seljuk Empire invaded Persia and became the first Turkic Muslim political power in Western Asia, kilij became the dominant sword form. The Iranian (Persian) shamshir was created during the Turkic Seljuk Empire period of Iran/Persia."
https://en.wikipedia.org/wiki/Kilij
Edit: a few pictures here:
https://www.pinterest.ch/thomaslothar/swords-of-the-umayyad-caliphate-era/?lp=true