William Stewart, in 1965, proposed the terms acrolect, the highest or most prestigious variety on the continuum, and basilect, the lowest or least prestigious variety, as sociolinguistic labels for the upper and lower boundaries, respectively, of a post-creole speech continuum.[1] In the early 1970s Derek Bickerton popularized these terms (as well as mesolect for intermediate points in the continuum) to refer to the phenomenon of code-switching used by some users of creole languages who also have some fluency in the standard language upon which the contact language is based.
See: https://en.wikipedia.org/wiki/Post-creole_continuum
