Tilly is an English pet form of Matilda, a Germanic name made up of maht, "might", and hild, "battle", so "mighty in battle". In Britain it has long been used as a given name in its own right and is a staple of the nursery-style names that came back in the 2010s. In the United States Tilly rose from number 2257 in 2015 to the top 1000 in 2024 and reached number 885 in 2025, its best rank ever.