The name Isadore has its origins in the Greek language and culture, dating back to ancient times. It is derived from the Greek words "isos" meaning "equal" and "doron" meaning "gift," collectively translating to "equal gift" or "gift of equality."

The earliest known record of the name Isadore can be traced back to the 4th century AD, when it was borne by Saint Isidore of Seville, a renowned scholar and philosopher who lived from 560 to 636 AD. He was an influential figure in the early Christian church and is recognized as the last scholar of the ancient world.

In the 7th century, the name Isadore gained prominence with Isidore of Miletus, a Greek mathematician and architect who is credited with the construction of the Hagia Sophia, one of the most magnificent and iconic buildings in Istanbul, Turkey.

Another notable figure with the name Isadore was Isidore of Kiev, a monk and scholar who lived in the 12th century and played a crucial role in the spread of Christianity in Russia. He is venerated as a saint in the Eastern Orthodox Church.

During the Middle Ages, the name Isadore was relatively uncommon but gained popularity in certain regions. One notable bearer of the name was Isidore the Farmer, a Spanish agricultural laborer who lived in the 12th century and is revered as the patron saint of farmers and rural communities in Spain.

In the 19th century, the name Isadore was associated with Isidore Geoffroy Saint-Hilaire, a French naturalist and zoologist who made significant contributions to the field of teratology, the study of birth defects. He lived from 1805 to 1861.

Over the centuries, the name Isadore has been borne by several other notable individuals, including Isidore Ducasse, a French poet and literary figure known by his pen name Comte de Lautréamont (1846-1870), and Isidore Isou, a Romanian-born French poet and playwright who founded the avant-garde movement Lettrism (1925-2007).