Old English tredan "to tread, step on, trample; traverse, pass over" (class V strong verb; past tense træd, past participle treden), from Proto-Germanic *tred- (source also of Old Saxon tredan, Old Frisian treda, Middle Dutch treden, Old High German tretan, German treten, Gothic trudan, Old Norse troða), from PIE *der- (1) "assumed base of roots meaning 'to run, walk, step'" [Watkins]. Related: Trod; treading. To tread water in swimming, "to move the feet and hands regularly up and down while keeping the body in an erect position in order to keep the head above the water" is attested by 1764.
Old English handle "a handle" (plural handla), formed from hand (n.) with instrumental suffix -el (1) indicating a tool in the way thimble was formed from thumb, spindle from spin, spindle from spin, ladle from lade, etc. The slang sense of "nickname" is first recorded 1870, originally U.S., from earlier expressions about adding a handle to (one's) name (1833), that is, a title such as Mister or Sir. To fly off the handle (1833) is a figurative reference to an ax head (to be off the handle "be excited" is recorded from 1825, American English). To get a handle on "get control of" is recorded by 1919.
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Definitions of treadle from WordNet
the brick maker treadles over clay to pick out the stones