Was curious why he was using a pseudonym and couldn't really find reasoning for it but did find Adams say

“That my Confessions may be compleat I must tell you that I wrote a very foolish unmeaning thing in Fleets Paper in 1762 or 1763 under the signature of Humphrey Ploughjogger. In this there was neither good nor Evil, yet it excited more merriment than all my other writings together”

Just a bit of merriment telling the entire colony some of the most racist shit possible