[mangamadaiyan]

Likely of British origin, during the Raj. I can imagine "Kindly do the needful, old chap" scrawled in the margin of an official missive, as it languidly flitted from one administrative table to another.

Many such anachronisms exist; thankfully, they're dying out one by one. A few decades ago (in the last century, to be precise), it wasn't very uncommon for official letters to be signed off with "I remain, Sir, your obedient servant". Later, it was shortened to "yours obediently"; it vanished altogether, thankfully.