Etymology
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twister (n.)
late 15c., "one who spins thread," agent noun from twist (v.). Meaning "tornado" is attested from 1881, American English.
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tongue-twister (n.)
1875, in reference to an awkward sentence, 1892 of a deliberately difficult-to-say phrase, from tongue (n.) + agent noun from twist (v.). The first one called by the name is "Miss Smith's fish-sauce shop."
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arm (n.1)

"upper limb of the human body," Old English earm, from Proto-Germanic *armaz (source also of Old Saxon, Danish, Swedish, Middle Dutch, German arm, Old Norse armr, Old Frisian erm), from PIE root *ar- "to fit together" (source also of Sanskrit irmah "arm," Greek arthron "a joint," Latin armus "shoulder"). Arm of the sea was in Old English. Arm-twister "powerful persuader" is from 1915. Arm-wrestling is from 1899.

They wenten arme in arme yfere Into the gardyn [Chaucer]
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