An officer who went before procession to clear the way by blowing a horn, or otherwise; hence, any person who marched at the head of a procession; a harbinger. [1913 Webster
" “Whifflers, or fifers, generally went first in a procession, from which circumstance the name was transferred to other persons who succeeded to that office, and at length was given to those who went forward merely to clear the way for the procession. . . . In the city of London, young freemen, who march at the head of their proper companies on the Lord Mayor's day, sometimes with flags, were called whifflers, or bachelor whifflers, not because they cleared the way, but because they went first, as whifflers did.” Nares.
"Which like a mighty whiffler 'fore the king,
Seems to prepare his way."