Samuel Johnson exhibited a rare lack of self-assurance when he gave this definition: "A disease, I suppose, of cattle".
We shall never know whether his supposition was justified, for the word has disappeared from our language; at least, the OED knows it not, though perhaps in some dark corner of rural Somerset that terrible scourge headgargle is still rife and therefore the word remains common currency.
Anyway, the doctor's doubts about its exact meaning did not prevent him from quoting the remedy: "For the headgargle, give powder of fenugreek. Mortimer." He does not tell us which Mortimer made this recommendation but it is worth committing to memory; every vegetarian cook worth his Noirmoutier salt has powder of fenugreek to hand (for flavouring his purée of mung beans) and should know how handy it will be if headgargle breaks out.