"turned or turning to the left," 1839, a word wanted by the botanists to describe the direction of spiral structures in nature, from Latin sinistrorsus "toward the left side," from sinister "left" (see sinister) + versus "turned," past participle of vertere "to turn" (from PIE root *wer- (2) "to turn, bend").
By 1837 in French. It was paired with dextrorse, but confusion over what was the proper point of view to reckon leftward or rightward spiraling (the observer or the observed) prevented the word being as useful as it might have been. The earlier adjective was sinistrorsal (by 1823).
updated on November 06, 2022