Small things matter!

Checks whether your package name is taken or available !!

install.packages("available")

library(available)
available("seer")

Warning: unable to access index for repository http://www.stats.ox.ac.uk/pub/RWin/src/contrib:
  cannot open URL 'http://www.stats.ox.ac.uk/pub/RWin/src/contrib/PACKAGES'

── seer ────────────────────────────────────────────────────────────────────────
Name valid: ✔
Available on CRAN: ✖ 
Available on Bioconductor: ✖
Available on GitHub:  ✖ 
Abbreviations: http://www.abbreviations.com/seer
Wikipedia: https://en.wikipedia.org/wiki/seer
Wiktionary: https://en.wiktionary.org/wiki/seer
Sentiment:???

This means the name seer is taken in both CRAN and GitHub.