"Tau" is by far the dominant name for the particle. I was in grad school when it was discovered. I wrote a Monte-Carlo simulation of ##\nu_\tau + N \rightarrow \tau + X## followed by ##\tau \rightarrow e + \bar \nu_e + \nu_\tau## decay in an attempt to find tau-neutrino events in the neutrino experiment that I was working with. I don't remember any of the papers that I read, or people I talked to, using the name "tauon." Nor do I specifically remember seeing the name in the 30+ years since then, although I've kept only peripheral touch with the field.
Nevertheless, a search on
http://scholar.google.com for "tauon" does turn up a number of hits, including published papers from 2010 and 2011 on the first page. So it's not unheard of.