The words "espouse" and "spouse" are related, both deriving from the Latin verb "spondēre," meaning "to promise or betroth." In fact, the two were once completely interchangeable, with each serving as a noun meaning "a newly married person" or "a husband or wife" and also as a verb meaning "to marry." Their semantic separation began in the 17th century, when the noun "espouse" fell out of use. Around the same time, people started using the verb "espouse" figuratively to mean "to commit to and support a cause." "Spouse" continued to be used in both noun and verb forms until the 20th century, when its verb use declined and it came to be used mainly as a noun meaning "husband or wife."
