Zackery is a variant of Zachary, from Hebrew meaning the Lord has remembered.
Zackery is a phonetic spelling variant of Zachary, which is itself the English vernacular form of the Hebrew Zechariah — meaning "God has remembered" — that became widespread in the English-speaking world through centuries of biblical familiarity and liturgical use. The standard English spelling Zachary emerged as the dominant form in American usage by the 19th century, but the spelling tradition around names beginning with the Zach- cluster has always been notably fluid: Zachery, Zackery, Zakary, and Zakery all appear in historical records, each representing a slightly different attempt to render the same sound in writing without the counterintuitive 'ch' digraph that the standard spelling requires.
The name's American prestige received its most durable boost from Zachary Taylor, the 12th President of the United States and hero of the Mexican-American War, whose popular nickname "Old Rough and Ready" made him a household name in the 1840s. The name thus acquired an unmistakably American frontier quality — rugged, unpretentious, military — that distinguished it from its more formally religious European forms. By the 1980s and 1990s, Zachary and its variants had become solidly popular middle-American given names, associated with suburban childhoods and youth sports leagues rather than prophets or priests.
The Zackery spelling specifically appeals to parents who want the phonetics to be immediately legible — the double-k making the hard-c sound unambiguous — while also marking a degree of individuality within a popular name cohort. It is the spelling equivalent of taking a well-traveled road and choosing the slightly less-worn parallel path: same destination, faintly different character.