One over the eight

What’s the origin of the phrase ‘One over the eight’?

This originated as UK military slang. The first reference to it in print is in Fraser and Gibbons’ Soldier and Sailor Words and Phrases, 1925:

“One over the eight, one drink too many. Slightly intoxicated, the presumption being that an average ‘moderate’ man can safely drink eight glasses of beer.”

After a gallon of beer ‘slightly intoxicated’ seems a bit of an understatement. Beer was weaker in the 1920s than it is now, but even so.

Other phrases first cited in Fraser and Gibbons:

Go Dolally
Jam tomorrow
Loaf of bread (head)

Other ‘One’ phrases:

One-hit wonder
One fell swoop - At
One for the road
One foot in the grave
One sandwich short of a picnic
One small step for man
One stop shop
One swallow doesn’t make a summer