The given name Marni has its origins in the Hebrew language. It is believed to be a diminutive form of the Hebrew name Miriam, which means "bitter" or "beloved". The name Miriam is found in the Bible, where it refers to the sister of Moses and Aaron.

Marni is thought to have emerged as a name in its own right during the Middle Ages, particularly in Italian and other Romance language-speaking regions. It may have been influenced by the Italian word "marna", meaning "marl" or a type of soil.

One of the earliest recorded instances of the name Marni can be found in the 13th century. Marni di Navarra was an Italian noblewoman who lived in the late 1200s and was known for her patronage of the arts and literature.

In the 15th century, Marni Baldassar was an influential Venetian philosopher and writer whose works explored themes of ethics and morality. She is considered an important figure in the Italian Renaissance.

During the 16th century, Marni Bianchi (1516-1594) was a renowned Italian painter and fresco artist. Her works adorned several churches and palaces in her native Florence.

In the 18th century, Marni Valsecchi (1724-1806) was an Italian mathematician and astronomer who made significant contributions to the study of celestial mechanics and the calculation of planetary orbits.

Another notable figure with the name Marni was Marni Karvosius (1856-1923), a Lithuanian-American writer and activist who campaigned for women's rights and social justice in the early 20th century.

Throughout history, the name Marni has been associated with individuals from diverse backgrounds, reflecting its enduring presence across various cultures and time periods.