出典:Wiktionary
From Middle English erraunt [and other forms],[1] from Anglo-Norman erraunt, from Old French errant, the present participle of errer (“to walk (to); to wander (to); (比喩的に) to travel, voyage”), and then:[2]
errant (comparative more errant, superlative most errant)
Although arrant is a variant of errant, their modern meanings have diverged. Arrant is used in the sense “complete; downright; utter” (for example, “arrant knaves”), while errant means “roving around; wandering” and is often used after the noun it modifies (for example, “knight errant”). The use of errant to mean “complete; downright; utter”, and arrant to mean “roving around; wandering”, is obsolete.