Kaileigh is a modern spelling of Kaylee, generally linked to Irish-derived sounds and meanings like 'slender' or 'fair.'
Kaileigh is one of the most orthographically elaborate entries in the extended family of Kaylee/Kayleigh variants — a name whose popularity represents one of the defining phenomena of Anglo-American naming in the 1980s and 1990s. The phonetic root may draw on several sources: the Irish name Cadhla (meaning 'beautiful,' pronounced roughly as 'Ky-la'), the Scottish Gaelic caol (narrow, slender), or the simple compound of the names Kay and Lee. The name exists primarily as a sound — a bright, two-syllable sequence — rather than as a bearer of a single clear etymology, which is itself a characteristic of the modern naming tradition.
The British progressive rock band Marillion significantly amplified the name's cultural presence with their 1985 hit single 'Kayleigh,' a bittersweet song about lost love that reached number two on the UK charts. The song fixed 'Kayleigh' as the 'standard' spelling in British consciousness, though American usage splintered into dozens of variants: Kaylee, Kayleigh, Kaylie, Kayly, Kailee, Kailey, Kaileigh, and more. Each variant represents a parental choice about how to individualize a name that was becoming increasingly popular — a paradox wherein the desire for uniqueness multiplied instances of essentially the same name.
Kaileigh specifically, with its 'K', 'ai', and 'eigh' — three distinct ways of rendering familiar sounds — is maximally inventive within this tradition. It reads as a name chosen by parents who loved the sound passionately enough to labor over the letters. Whatever it lacks in etymological depth it compensates for in orthographic personality. In a classroom full of Kaylees, a Kaileigh is immediately recognizable — which was, perhaps, always the point.