before vowels psil-, word-forming element meaning "stripped, bare," used mostly in forming scientific terms, from Greek psilos "bare, naked; mere," perhaps akin to psēn "to rub," and both or either perhaps from PIE root *bhes- "to rub" (source also of Greek psamathos "sand;" see sand (n.)). Middle English had psilotre "a depilatory ointment" (c. 1400).

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