Do you happen to know who coined the term and when?
I’ve an awful feeling this may be a term that I myself had a hand in inventing, although I can’t remember the details.
It is not recorded in the on-line OED, whether under “pre-fortis” or under “clipping”.
As far as I remember, it was decided on by a group of phonetics teachers at UCL (probably Michael Ashby, John Maidment, Jill House, and me), sometime in the mid 1980s. This was shortly after the retirement or death of the previous generation of UCL phoneticians (Fry, Gimson, O’Connor, Arnold, Tooley and Pring).
The reason for seeking a new term for the phenomenon was that we found the term “shortening”, as applied to English vowels, unsatisfactory. A “shortened” /iː/, as in reach, is not the same as “short” /ɪ/, as in rich. “Shortened” (i.e. clipped) /ɔː/, as in court, is not the same as short /ɒ/, as in cot. Gimson’s term “reduced” was also confusing, since reduction is generally understood as a synonym of weakening or lenition.
So, rather than speak of “shortened” or “reduced” vowels, we thought it would be better to refer to them as clipped vowels.
I did not use the term “pre-fortis clipping” in Accents of English (1982) — which I presumably would have done had it been available then — but I did use it in the first edition of LPD (1990), as well as in my article ‘Syllabification and allophony’ published in Susan Ramsaran (ed.), Studies in the pronunciation of English, A commemorative volume in honour of A.C. Gimson (London and New York: Routledge, 1990), pages 76-86, where I said of Pre-fortis clipping
This is the name which some of us have come to adopt for the rule making the /el/ of shelf durationally different from the /el/ of shelve, and the /iː/ of feet different from that of feed. (Gimson refers sometimes to ‘shortness’ of the sounds involved, sometimes to ‘reduction’. Calling such sounds ‘short’ leads to confusion when pairs of phonemically distinct vowels such as /iː/ and /ɪ/ are also categorised as ‘long’ and ‘short’ respectively; calling them ‘reduced’ is to be avoided since this term for most phoneticians denotes change of quality, a ‘reduced’ vowel being of the [ə] type. The term ‘clipping’ avoids these difficulties.)
English vowels are subject to pre-fortis clipping, then, when they are followed by a fortis consonant within the same syllable. The /f/’s in self, selfish /ˈself.ɪʃ/, and dolphin /ˈdɒlf.ɪn/ trigger clipping, but not those in shellfish /ˈʃel.fɪʃ/ or funfair /ˈfʌn.feə/. So do the /t/ in feet and the /ʧ/ in feature, but not the /p/ in fee-paying or the /k/ in tea-kettle. The vowel /æ/ undergoes pre-fortis clipping in lap, lamp, happy /ˈhæp.ɪ/, and hamper /ˈhæmp.ə/, but not in slab or clamber.
Does anyone know of an appearance in print prior to 1990?