Use of the term originates from a 19 September 2014 strip of the webcomic Wondermark by David Malki titled The Terrible Sea Lion,cwhere a character expresses a dislike of sea lions and a sea lion intrudes to repeatedly ask her to explain her statement and attempts (in an exaggeratedly civil manner) to interrogate her views, following the characters into the privacy of their own home. “Sea lion” was quickly verbed, and noting this, Malki posted on his own Wondermark site, “I’m happy that it’s resonated with so many people”.

en.wikipedia.org/wiki/Sealioning