arid

English arid comes from French aride or directly from Latin āridus, 'dry, arid, parched.' That Latin adjective was built from the verb āreō, 'to be dry, to be parched,' tracing back through Proto-Italic to a Proto-Indo-European root meaning to be dry.

The word began as a description of the state of being dry (āreō) and, with the addition of a Latin adjective-forming suffix, hardened into āridus, a word for something parched — a form that passed through French largely unchanged into English.

It's akin to Latin ārdeō, 'to be on fire, to burn' — so the word for dryness and the word for burning likely share a deep root, dryness and fire being close cousins in meaning.