Have you checked the book Mastering Turbo Debugger by Tom Swan available here
Quote:
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https://bitsavers.org/pdf/borland/turbo_debugger/Swan_Mastering_Turbo_Debugger_1991.pdf
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In the acknowledgement is mentioned "To Turbo Debugger's developers at Purart, especially Chris Williams: Thanks for an excellent debugger". So maybe Purart is a good lead