The abbreviations D.D. or similar for Doctor of Divinity and L.L.D. for Legum Doctor or Doctor of Laws are somewhat older than M.D. or Ph.D.. For example, the 21st edition of Nathan Bailey's An universal etymological English dictionary, printed in 1675, shows T.D. in the entry after fifth SYZYGIA entry, and shows L.L.D. after LIZEN'D. More @Wikipedia
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