Frosty

wiktionary

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From Middle English frosty, forsty, from Old English forstiġ, fyrstiġ(“frosty”), from Proto-West Germanic *frostag, *frustīg, equivalent to frost +‎ -y. Cognate with West Frisian froastich(“frosty”), Dutch vorstig(“frosty”), German Low German fröstig(“frosty”), German frostig(“frosty”), Swedish frostig(“frosty”). Compare also Saterland Frisian froasterch(“frosty”), German Low German frösterg(“frosty”).

etymonline

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frosty (adj.)

Old English forstig, fyrstig "as cold as frost;" see frost (n.) + -y (2). Figurative use from late 14c. Related: Frostily; frostiness. Similar formation in Dutch vorstig, German frostig.