What is the origin of testudinate?

Testudinate derives from the Latin adjective testūdinātus, of the same meaning, from the noun testūdō “tortoise.” Testūdō, in turn, derives from testa “earthenware vessel; shard of baked clay; shell of a crustacean.” It is possible that testa comes from the Proto-Indo-European root ters- “dry,” which would make testa cognate to the words thirst (from Old English thurst “dryness”), terrain and terrestrial (from Latin terra “(dry) land”), and toast and torrid (from Latin torrēre “to burn”). In Late Latin, testa gained the additional sense of “skull” and developed into the word for “head” in several Romance languages (such as French tête and Italian testa). Testudinate entered English in the early 1700s.