alacrity [əˈlækrɪti] n.
1.) Cheerful willingness; eagerness.
2.) Speed or quickness; celerity (American Heritage Dictionary of the English Language).
Etymology: Latin alacritas, from alacer, lively.
"And having thus displayed more sagacity than Butler expected from him, he courteously touched his gold-laced cocked hat, and by a punch on the ribs, conveyed to Rory Bean, it was his rider's pleasure that he should forthwith proceed homewards; a hint which the quadruped obeyed with that degree of alacrity with which men and animals interpret and obey suggestions which entirely correspond with their own inclinations" (The Heart of Midlothian, Walter Scott, 1818).