To make something light, airy, or heavenly; to give something a spiritual or immaterial quality.
From ethereal plus -ize (American English suffix forming verbs). The -ize ending comes from Greek -izein and became standardized in American English spelling.
American English chose -ize over -ise partly because -ize has more direct ties to Greek origins, and this choice became a defining marker of American versus British English — just like how you can spot a word's origin by its spelling.
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