crowdy-headed jock, n. — Green’s Dictionary of Slang

crowdy-headed jock n.

[Scot./northern dial. crowdy, a gruel made from milk and meal; thus a porridge + Jock n. (1)]

a North Country seaman, esp. a collier.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Jock, or Crowdy-headed Jock. A jeering appellation for a North Country seaman, particularly a collier; Jock being a common name, & Crowdy the chief food among the Northumbeerland people of the lower order.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum [as cit. 1788].
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue [as cit. 1788].