"penis," 1969, from Yiddish shlang, literally "snake." Compare schmuck. As a verb, "to have sex with," by 2005. Related: Schlonged; schlonging. It does have a verbal usage, but strangely it says it started to be used in 1969. The linked Ngram Viewer seems to support it. What is its etymology? How did it get its traction? More @Wikipedia
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