One “parochial” constraint in Germanic is the absence of branching onsets consisting of a coronal stop followed by /l/. Thus /pl, bl, kl, gl/ are all common in Germanic, but *tl and *dl are not. It is difficult to understand what might gives rise to this phonotactic gap.

Blevins & Grawunder (2009), henceforth B&G, note that in portions of Saxony and points south, *kl has in fact shifted to [tl] and *gl to [dl]. This sound change has been noted in passing by several linguists, going back to at least the 19th century. This change has the hallmarks of a change from below: it does not appear to be subject to social evaluation and is not subject to “correction” in careful speech styles. B&G also note that many varieties of English have undergone this change; according to Wright, it could be found in parts of east Yorkshire. Similarly, no social stigma seems to have attached to this pronunciation, and B&G suggest it may have even made its way into American English. B&G argue that since it has occurred at least twice, KL > TL is a natural sound change in the relevant sense.

Of particular interest to me is B&G’s claim that one structural factor supporting *KL > TL is the absence of TL in Germanic before this change; in all known instances of *KL > TL, the preceding stage of the language lacked (contrastive) TL. While many linguists have argued that TL is universally marked, and that its absence in Germanic is a structural gap in the relevant sense, this does not seem to be borne out by quantitative typology of a wide range of language families.

Of course, other phonotactic gaps, even statistically robust ones, also are similarly filled with ease. I submit that evidence of this sort suggests that phonologists habitually overestimate the “structural” nature of phonotactic gaps.

References

Blevins, J. and Grawunder, S. 2009. *KL > TL sound change in Germanic and elsewhere: descriptions, explanations, and implications. Linguistic Typology 13: 267-303.