[...] the alternant pronunciations of 'duty' (1) /duwtiy/ and (2) /dyuwtiy/ carry certain distinct connotations. In some circumstances the form /dyuwtiy/ induces an unfavorable response from the listener, who interprets it as pedantic or associated with people whose culture he does not appreciate. On the other hand, among a certain small set of speakers of American English the form /duwtiy/ is a mark of educational and cultural inferiority.
- Nida (1949), a pag.151

Alternants such as 'shown' and 'showed' indicate that there is a meaningful difference between such allomorphs. [...] The contrast in meaning between the allomorphs '-en' and '-ed' is primarily one of connotation. The productive suffix '-ed', having an expanding distribution, is less acceptable in traditional contexts than the suffix '-en'. This is a matter of appropriateness and involves the reactions of the speakers and hearers. There is nothing intrinsic about the semantic values; they are dictated simply by the reactions of language-users to the sociolinguistic environment.
- Nida (1949), a pag.151-152

Almost as important as the objective symbolization of the various aspects of the environment is the subjective evaluation of these symbols. The objective part of symbolization we call denotation and the subjective part we term connotation.
- Nida (1949), a pag.152