Definition of "bulchin"

And better yet than this, a bulchin two years old

1612, Michael Drayton, Poly-Olbion

Wouldſt thou not haue ſome Bulchin from the herd / To phyſicke thee of this venereall itch?

1637, Tho[mas] Heywood, “Ivpiter and Io”, in Pleasant Dialogues and Dramma’s, Selected out of Lucian, Erasmus, Textor, Ovid, &c. […], London: […] R. O[ulton] for R. H[earne], and are to be sold by Thomas Slater […], page 170