Diminutive of Irene or René; Irene from Greek eirene meaning 'peace,' René from Latin renatus 'reborn.'
Rennie functions simultaneously as a diminutive of the French René or Renée and as a Scottish and English surname-turned-given-name, the two traditions reinforcing each other to produce a name with unusual depth. René derives from the Latin Renatus, meaning reborn — a name with deep Christian resonance, referring to spiritual rebirth through baptism. The concept was powerful enough to make René one of the most characteristic French names of the Catholic tradition, while Renée carried the same meaning into the feminine sphere.
Rennie softens either into something more intimate and less formally French. The most celebrated bearer of the name as a surname-given-name is Charles Rennie Mackintosh, the Scottish architect and designer who worked at the turn of the twentieth century and whose work remains among the most distinctive expressions of Art Nouveau in Britain. Mackintosh's integrated vision — buildings, interiors, furniture, typography, textiles all conceived as unified wholes — made his double-barrelled name famous across the design world.
His wife Margaret Macdonald was his creative equal and collaborator, and together they shaped what became known as the Glasgow Style. The name Rennie, through this association, carries connotations of artistic integrity and modernist vision. As a given name, Rennie has a pleasing gender-neutrality that suits contemporary naming sensibilities without feeling invented or forced — it arrives already worn smooth by history. The rebirth etymology gives it quiet optimism, while its sound sits comfortably beside Benny, Jenny, and Penny in the warm diminutive tradition of English naming.