When John Wycliffe's followers gained support from the common people, why did the church call them Lollards? What does Lollard mean? Why didn't they just call them Wycliffites?
According to the Oxford English Dictionary, Lollard means: "From M[iddle] [Dutch] lollaerd, lit. 'mumbler, mutterer', f[rom] lollen to mutter, mumble".
This was a pejorative term to refer to a CLASS of people that held certain religious beliefs, as opposed to holders of the beliefs themselves. Specifically, it referred to "uneducated" Englishmen (in the traditional sense), who had never been trained in the "catechism" in Latin, and therefore were considered to have "no basis" for their beliefs. Hence the designation Lollards, or "mumblers."
Wycliffe HAD been trained in the traditional way, and chose to deviate. Calling his followers "Wycliffites" was considered "too kind," when most of them could be attacked on grounds of "ignorance," as opposed to merely the "unsoundness" of their beliefs.
The name was derived from lollium, a tare, but was used in Flanders early in the fourteenth century to refer to one as a "hypocrite". Others took it to mean "idlers" and connected it with to loll.
In the fourteenth century the word "lollard" was used to represent a number of terms. People who were identified as anti-clerical and wishing to disendow the Church, tenants of an unpopular abbey, or parishioners who refused to pay their tithes, would often be called Lollards as well as fanatics.
There is a very lengthy discussion on the topic here.