To cite the 'gender' package, you may either cite the package directly or cite the journal article which explains its method:

Lincoln Mullen (2018). gender: Predict Gender from Names Using Historical Data. R package version 0.5.2.

For the journal article, please cite: Cameron Blevins and Lincoln Mullen, "Jane, John ... Leslie? A Historical Method for Algorithmic Gender Prediction," _Digital Humanities Quarterly_ 9, no. 3 (2015): <http://www.digitalhumanities.org/dhq/vol/9/3/000223/000223.html>.

Corresponding BibTeX entry:

  @Manual{,
    title = {gender: Predict Gender from Names Using Historical Data},
    author = {Lincoln Mullen},
    year = {2018},
    note = {R package version 0.5.2},
    url = {https://github.com/ropensci/gender},
  }