From Latin 'recūsāre' (to push back), via Anglo-Norman — reversed from driving others back to driving oneself forward.
To move with urgent haste.
From Anglo-Norman 'russher' meaning 'to drive back, to repel,' from Old French 'ruser' (to dodge, repel), from Latin 'recūsāre' (to refuse, push back). The sense shifted from driving others back to driving oneself forward. Key roots: recūsāre (Latin: "to refuse, drive back").
'Rush hour' first described the 1890s crush of commuters — the phrase transferred the urgency of a gold rush to daily urban life.