Green’s Dictionary of Slang

soldiers bold n.

also soldier’s bold
[rhy. sl.]

(Aus./N.Z.) a (head) cold.

[Aus]Sport (Adelaide) 3 Aug. 14/3: They Say [...] That Ned H. had a severe ‘soldier’s bold,’ and did not dance at the social.
[Aus]R. Aven-Bray Ridgey-Didge Oz Jack Lang 43: Soldiers Bold Cold.
[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 172/2: soldiers bold n. 1 a cold.