It is quite interesting that the 4-gram things spur so much
interest. I guess there are many motivations in borrowing terms:
for technical communication (medical terms), an inclination or romance of
the great Roman empire in the Renaissance period (e.g. debt (b or t?
added because the word would look like Latin! - references below)).
Robert Luk
Scragg (1975) A History of English Spelling, Manchester University Press, Manchester
Venezky (1970) A Study of English Spelling-to-Sound Correspondences on Historical Principles, Ann Arbor Press, Ann Arbor, MI.