unstinting

From un- (prefix meaning ‘not’) + stint (“to be mean or sparing”) + -ing (suffix forming present participles of verbs), or un- + stinting (“mean, sparing”). Stint is derived from Middle English stinten, from Old English styntan (“to make blunt”) and *stintan (attested in āstintan (“to assuage; to make dull; to stint”)), from Proto-West Germanic *stuntijan (“to make dull; to shorten”), from Proto-Germanic *stuntijaną (“to make dull; to shorten”) and Proto-Germanic *stintaną (“to make short”), ultimately from Proto-Indo-European *(s)tewd- (“to hit; to push”), probably influenced by Old Norse *stynta, stytta (“to make short, shorten”).

来源：wiktionary