Green’s Dictionary of Slang

(UK Und.) a newly enlisted soldier.

1703		Hell Upon Earth 6: Swad or Swadkin, a Soldier.
1708		J. Hall Memoirs (1714) 14: Swad, or Swadkin, a Soldier.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1867		W.H. Smyth Sailor’s Word-Bk (1991) 668: Swad, or Swadkin. A newly raised soldier.