c. 1200, "to knock down" using a sling, later "to throw" (mid-13c.), especially with a sling, from Old Norse slyngva, from Proto-Germanic *slingwanan (source also of Old High German slingan, German schlingen "to swing to and fro, wind, twist;" Old English slingan "to creep, twist;" Old Frisian slinge, Middle Dutch slinge, Old High German slinga, German Schlinge "sling;" Middle Swedish slonga "noose, knot, snare"), from PIE *slengwh "to slide, make slide; sling, throw." Meaning "to hang from one point to another" (as a hammock) is from 1690s. Related: Slung; slinging.
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Harper, D. (n.d.). Etymology of slinger. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/slinger