The word 'ungrudging' is built upon the negative prefix 'un-' attached to the present participle form of the verb 'grudge'. The core morpheme 'grudge' entered Middle English from Old French, carrying the sense of murmuring in complaint or giving with reluctance. By adding the '-ing' suffix, it forms an adjective describing the action of the verb. The prefix 'un-' directly reverses this meaning, creating a term that describes an action performed without any hint of resentment or unwillingness, thus embodying a spirit of cheerful and wholehearted generosity.

Structure: un (not) + grudg (to complain or be unwilling) + ing (adjective suffix) - un: A prefix of Germanic origin (Old English) meaning "not," used to form negatives. - grudg: A morpheme from the Middle English verb 'grudgen' or 'grucchen', meaning to murmur, complain, or give reluctantly. Its ultimate origin is uncertain but may be related to Old French 'grouchier'. - ing: A suffix of Germanic origin (Old English '-ende', '-ing') used to form present participles and adjectives from verbs.