Plonk

Abbreviated from the French "vin blanc" meaning white wine, this typical British soldier's alliteration eventually became the word for any kind of wine, as in, "pass that bottle of plonk".

Binge

Continuing with the theme of alcohol, binge was originally a Lancashire term meaning to over-indulge. Whilst the word can have negative connotations around food and drink, it's also used to describe life-affirming entertainment - from shamelessly listening to podcasts back-to-back, to watching the entire run of your favourite TV series in one sitting. Bliss.

Having a chat/chatting

Soldiers from the Commonwealth were often billeted with the British "Tommies", and that included several regiments from India. Whilst the word was used way back (e.g. evidence of its use can be found in Shakespeare's Romeo and Juliet), it's popularity grew, in this instance, from the Hindi word for parasite ("chat").

As the prevalence of lice was an everyday problem at the front, men sitting around picking them off their skin led to such groups being described as men "chatting". In later years this has morphed into the term "chatting" or "having a chat" to mean a group of people, or even two people, sitting around casually talking to each other.

Crummy

Lice were also directly responsible for this American slang term coined by US infantrymen, meaning lousy or of inferior quality. The eggs of the lice were white and resembled tiny crumbs of bread, hence the word "crummy".