Actually, RVW 1908.
Pooks have little etymology, but came to attention with Kipling in 1906, so the likelihood is it's very close to those dates.
Thematically, it takes off from where Outlandish Knight left off, for all that I argue the coda is borrowed from someone's version of Young Hunting, both found in Arthur Quiller Couch's 1910 Oxford Book of Ballads. One might think, perhaps, that unknitting the former left a hole which Lovely Joan fills.