Kasiah is likely related to Kassia or Keziah, from Hebrew roots associated with cassia, a fragrant spice.
Kasiah is a lyrical variant of Keziah — itself an ancient Hebrew name from the Old Testament. Keziah (קְצִיעָה, Qetsîʿâh) means "cassia," the fragrant bark of a tree related to cinnamon, prized throughout the ancient Near East as a spice, a perfume ingredient, and a component of the sacred anointing oil described in Exodus. In the Book of Job, Keziah is the name of one of Job's three daughters born to him after his trials — daughters described as the most beautiful women in all the land, to whom their father gave an inheritance alongside their brothers, an unusual and telling detail in the context of ancient inheritance law.
The name enjoyed use in Puritan England and colonial America, where Old Testament names — especially those of minor but evocative figures — were fashionable as expressions of scriptural piety. It appeared in American records through the 18th and 19th centuries before falling into relative obscurity. The variant spellings Cassia, Kesia, and Kasiah emerged as parents discovered the name anew and adapted its orthography for modern sensibilities.
Kasiah in particular gives the name a flowing quality, the -iah ending echoing the patterns of Hebrew theophoric names like Isaiah and Jeremiah. In the contemporary naming landscape, Kasiah occupies a compelling niche: it is recognizably ancient yet feels fresh and unhackneyed, carrying the warmth of spice and fragrance in its very etymology. The imagery of cassia — aromatic, golden-barked, associated with beauty and sacred ritual — makes it a name that rewards reflection. Parents drawn to Biblical names with a softer, more unusual profile are increasingly rediscovering it.