Meaning

adjective not in action or at work

verb run disconnected or idle

noun the state of an engine or other mechanism that is idling

originFrom Middle English idel, ydel, from Old English īdel, from Proto-West Germanic *īdal, from Proto-Germanic *īdalaz. Cognate with Dutch ijdel (“vain, meaningless”), ijl (“rareified, skinny”), iel (“thin, slender”); German Low German iedel (“vain, idle”); German eitel (“vain, conceited”); and possibly Old Norse illr ("bad"; > English ill).

Etymology from Wiktionary, CC BY-SA 3.0