The term originally referred to a calfskin stuffed with straw and presented to a cow, as if living, to induce her to give milk.
The epithet Tulchan applied to the bishops is usually ascribed to the reformer and collector of Scottish proverbs David Fergusson.
[1] Mr. Gladstone, during his electioneering raid into Midlothian in November 1879, explained the meaning of "tulchan", which he spelt "tulcan": Jamieson writes the word "tulchane", and cites the phrase, "a tulchane bishop", as the designation of one who received the episcopate on condition of signing the temporalities to a secular person.
One of them, Robert Montgomery (before 1550–1609), was prosecuted by the religious reformer Andrew Melville (1545–1622).
Jamieson further states: In other words, a "tulchan" can also be a living animal, and the usage is of one who gains profit by pretending to be someone, or something else.