According to both my trusted sources (wiktionary and etymonline), the word debt (“something owed”) traces to the Middle English word dette, which goes back to dett, from the French etymon dete. I was wondering how a silent b got placed into the word; how come we don’t have det or something similar? I know the Latin word this stems from was debere; did this influence the evolution of the word, or was some medieval scholar trying to be fancy, as occurred to so many similar words?
The etymology in my edition of the OED is given as follows, and confirms your suspicion.
Middle English dette: from Old French, based on Latin debitum ‘something owed’, past participle of debere ‘owe’. The spelling change in French and English was by association with the Latin word.
So indeed, the spelling inherited from Old French was modified by influence of Latin. This most likely occurred during the Renaissance, or even slightly later, with the renewed interest in the Classical (Latin) world. Many spellings were modified from around the 15th century to the 19th century under this influence, reverting the pronunciation shifts reflected by the vulgarisation of Latin over many centuries, which very often included dropping of (hard) vowels or elision of silent hs, to name but a couple of changes.
In fact, this phenomenon wasn’t limited to English, and was extremely prevalent in Spanish (albeit much less so in Italian).