Crust

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Middle English: from Old French crouste, from Latin crusta ‘rind, shell, crust’.

wiktionary

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From Middle English cruste, from Anglo-Norman and Old French cruste, from Latin crusta(“hard outer covering”), from Proto-Indo-European *krustós(“hardened”), from *krews-(“to form a crust, begin to freeze”), related to Old Norse hroðr(“scurf”), Old English hruse(“earth”), Old High German hrosa(“crust, ice”), Latvian kruvesis(“frozen mud”), Ancient Greek κρύος(krúos, “frost, icy cold”), κρύσταλλος(krústallos, “crystal, ice”), Avestan 𐬑𐬭𐬎𐬰𐬛𐬭𐬀-‎ (xruzdra-, “hard”), Sanskrit क्रूड्(krūḍ, “thicken, make hard”)

etymonline

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crust (n.)

early 14c., "hard outer part of bread," from Old French crouste (13c., Modern French croûte) and directly from Latin crusta "rind, crust, shell, bark," from PIE *krus-to- "that which has been hardened," suffixed form of root *kreus- "to begin to freeze, form a crust." From mid-15c. as "any hard, external portion of comparative thinness;" meaning "outer shell of the earth" is from 1550s.

crust (v.)

late 14c., "to thicken or contract into a hard covering" (intransitive); see crust (n.). From 1540s in transitive sense of "cover with a crust or hard exterior portion." Related: Crusted; crusting.