From the Indianapolis Business Journal:
Playing the name game
The first erectile dysfunction drugs to make U.S. debuts also cornered the market on manliness. Pfizer Inc.'s Viagra evokes images of power and fluid motion, like mighty Niagara Falls, said branding consultant Anthony Shore.

Levitra, developed by Bayer Pharmaceuticals and GlaxoSmithKline Plc, also connotes power and, of course, levitation or elevation, Shore added.

The third entrant, Cialis, dared to be different. The name of that drug, developed by Indianapolis-based Eli Lilly and Co. and Bothell, Wash.-based ICOS Corp., tugs at the heartstrings.