Undress

wiktionary

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From Middle English undressen, equivalent to un- +‎ dress. Compare Old English unsċrȳdan(“to undress”, literally “un-shroud”).

etymonline

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undress (v.)

1590s, "to shed one's clothing," from un- (2) "opposite of" + dress (v.). Transitive sense of "to strip off (someone's) clothing" is recorded from 1610s. Related: Undressed; undressing.

undress (n.)

"state of partial or incomplete dress," 1680s, from undress (v.). Meaning "ordinary dress" is from 1748.