Tireless means never seeming to grow weary. A tireless campaigner, tireless work, tirelessly cheerful.
It is always praise and it is nearly always attached to somebody working for others — tireless campaigner is close to a fixed phrase in obituaries and citations. It describes the appearance rather than the fact, since nobody is actually tireless. Note that -less means without, as always.
1adjectivetirelessNever seeming to grow weary.
“Thanks to her tireless work, the village finally got a new school.”
synonyms: indefatigable, untiring
tireless is a quality of endurance.
Middle English
tiren
English
tire
English, today
tireless
Built from
From tire + -less. tire comes from Middle English tiren. From Middle English tiren, tirien, teorien, from Old English tȳrian, tēorian (“to fail, cease, become weary, be tired, exhausted; tire, weary, exhaust”), of uncertain origin. Possibly from Proto-West Germanic teuʀōn (“to cease”), which is possibly from Proto-Indo-European dews- (“to fail, be behind, lag”). Compare Ancient Greek δεύομαι (“to lack”), Sanskrit दोष (“crime, fault, vice, deficiency”).
Etymology from Wiktionary, CC BY-SA