The early German reformers and the followers of Wickliffe were so called. An ingenious derivation is given by Bailey, who suggests the Latin word lolium (darnel), because these reformers were deemed “tares in God's wheat-field.”
Gregory XI., in one of his bulls against Wickliffe, urges the clergy to extirpate this lolium.
“The name of Lollards was first given (in 1300) to a charitable society at Antwerp, who lulled the sick by singing to them.” —Dr. Blair: Chronology (under the date 1300).
German lollen, to hum.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894