On 23 Aug, 03:09, Nyal Williams wrote:
Early on, compasses were filled with alcohol and they were referred to as
"spirit" compasses -- a common descriptor for volatile substances.
This, together with the word "spirits" used for distilled liquor, led to
using the phrase "whiskey compass." (My guess is as good as yours.)

My handbearing compass for sailing - a Sestrel - is filled with gin!

Ian