The firm said it felt the new name "better represents" its fund management arm and "reflects its evolution" from its original unit trust offering to a wider range of funds and structures available to investors.
CEO Tom Carroll said the new name was a "better fit" for a business which manages over £12bn of assets, and which has "significantly broadened" its range of strategies beyond the unit trusts available originally.
Rathbones and Investec W&I complete merger to create £100bn wealth manager
Carroll said the firm's aim was to offer further strategies across more asset classes in the future where it identifies significant client demand, as well as an opportunity to "provide something different for investors of all types".
"We remain true to our culture, where small independent teams are empowered to actively invest and deliver for our clients, with accountability for their decisions," he said.
"RAM combines the flexibility and teamwork of an investment boutique with the advanced infrastructure, governance and oversight afforded by being part of a large, patient parent in the Rathbones Group."
Rathbones flows fall flat as Investec W&I merger completes
Carroll took over as CEO of Rathbones' funds business from Mike Webb, who is set to retire at the end of this year after 14 years in the position.
The rebrand follows Rathbones' acquisition of Investec Wealth & Investment in a £839m deal, which was completed in September, creating one of the largest discretionary wealth managers in the UK with £100bn in combined assets.
Investec W&I now operates under the Rathbones brand with Investec Group as a long-term, strategic shareholder. Following the combination, Investec now has an economic interest of 41.25% in Rathbones' enlarged share capital.