wax: Common Errors in English Usage Entry for Friday, March 16, 2012

wax
 An unusual use of the word “wax” is “to change manner of speaking,” as in “she waxed eloquent on the charms of New Jersey” or “he waxed poetic on virtues of tube amplifiers.” These expressions mean that she became eloquent and he became poetic. It is an error to say instead “she waxed eloquently” or “he waxed poetically.”