hullo

The word 'hullo' is a chiefly British variant of the greeting 'hello,' which itself emerged in the late 19th century. Its ultimate origin is obscure, but it is often traced to an alteration of the older call 'hollo' or 'halloo,' used to attract attention or urge on hounds. 'Hollo' itself may derive from the Old French hunting cry 'hau!' and related Germanic shouts. The shift from a loud call to a standard greeting represents a semantic narrowing and conventionalization of a spontaneous exclamation into a social formula.

The word is a simplex variant of "hello," likely formed by alteration. It is not productively composed of smaller, meaningful morphemes in modern English.