Curiously, we had the same confusion yesterday with Greek και (kai), which, like et, can serve as a conjunction meaning “and”, but can also be used adverbially to mean “also” or “even” or as here simply to emphasize the word that follows.
http://discourse.textkit.com/t/xenophon-1-3-18-19/14074/1
As in the και thread, I think it might be helpful to skim the dictionary entry–in this case, Lewis and Short–for et to see the full range of uses to which this word can be put.
http://perseus.uchicago.edu/cgi-bin/philologic/getobject.pl?c.4:1256.lewisandshort