What is the origin of estivate?

Estivate has two main senses: “to spend the summer at a specific place or in a certain activity” (as at the beach or in the mountains), and a zoological sense, “to spend a season in a dormant state, as certain reptiles and small mammals” (the “opposite,” as it were, of hibernate). Estivate comes from Latin aestīvātus, the past participle of aestīvāre “to reside during the summer.” Aestīvāre is a derivative of the adjective aestīvus “of or relating to summer; summery,” itself a derivative of the noun aestās “summer.” The Proto-Indo-European root behind the Latin words is ai– “to burn,” which is also the source of Latin aestus “heat, hot weather, hot season,” aedēs “dwelling place, abode, home” (because it was heated), and aedificium “a building” (English edifice). Two other derivatives, aedificāre “to erect a building,” and aedificātiō “the act or process of erecting a building; the building itself,” in Christian Latin developed the senses “to develop spiritually, improve the soul” (and “spiritual growth” for the noun), in current English edify and edification, which nowadays have nothing at all to do with the building trades. Estivate entered English in the first half of the 17th century.