On the Q T

Does anyone know the origin of this? My husband says it means "on the Quiet", in other words you got something on the sly

MW says it is an abbreviation for "quiet":

Main Entry: q.t.
Pronunciation: "kyü-'tE
Function: noun
Usage: often capitalized Q&T
Etymology: abbreviation
Date: circa 1887

QUIET -- usually used in the phrase on the q.t.