Usage Note: The adverb thusly was created in the 1800s as an alternative for thus in sentences such as Hold it thus or He put it thus. It appears to have been first used by humorists, who may have been imitating the speech of poorly educated people straining to sound stylish. The word has subsequently gained some currency in educated usage, but it has long been deplored by usage commentators as a “nonword.” A large majority of the Usage Panel found it unacceptable in 1966, and this sentiment was echoed nearly forty years later in our 2002 survey, in which 86 percent of the Panel disapproved of the sentence His letter to the editor ended thusly: “It is time to stop fooling ourselves.”
- thus (in this way).
Although thusly has diffused into popular usage, it is still widely regarded as incorrect; instead, other equivalent expressions (such as thus or this way) can be used. It originated in the Eastern U.S., and it is still more common in American than British English; it is "often used for amusement or to make an ironic point."