Green’s Dictionary of Slang

mouldy adj.

also blue mouldy, moldy

1. [late 16C+] useless, second-rate, out-of-date.

2. [mid-19C] grey-haired.

3. [late 19C–1970s] boring, gloomy, sick.

4. [1930s+] (also mowldy) very drunk.

In compounds

mouldy one (n.) (also mouldy, mouldy coin, mouldy ’un, moulie) [the colour]

1. [mid-19C–1950s] a copper coin.

2. [1900s] (Aus.) a punch, a blow.

mouldy pate (n.) [SE pate]

[mid–late 19C] a servant wearing a grey powdered wig.

In phrases

blue mouldy (adj.) (also ...for a fight)

[mid-19C+] (Irish) stale, out of condition; thus phr. blue mouldy for want of a beating, looking for a fight, win or lose.