Oxymel (from Latin 'acid and honey', from Ancient Greek ὀξύς 'acid' and μέλι 'honey') is a mixture of honey and vinegar, historically used as a medicine.
Its name is often found in Renaissance (and later) pharmacopoeiae in Late Latin form as either a countable or uncountable noun. As a countable noun, it is spelled variously as (singular) oxymellus[citation needed] and oxymellis, and plural oxymeli and oxymelli.
Cato the Elder describes it thus:
Oxymelli. Fit vinum ex aceto & melle quod oxymel vocaverunt voce Graecanica. Nam oξ(?) dicitur Graecis acetu & μίλ mel. Fit autem oxymel hoc modo. Mellis decem librae cum aceti heminis quinque, haec decies subserve faciunt atque ita sinunt inveterare. Themison summus autor damnavit oxymel & hydromel. Est autem hydromel vinum ex aquae & melle confectum, unde & nome. Celebrant autores ex omphacomel, quod fit ex uvae semiacerbae succo & melle fortiter trite unde & nome: Graec enim όμφας dicitur uvae acerbae, & όμφαφκας vocant uvas & fructus immaturus. Hinc omphalicium oleum dictum, quod ex olivis acerbis quas δίγρας(?) vocant, fit: & omphacium ex uva, quod vulgo agreste nominitant.
— Cato, reproduced by Columella, De Re Rustica
In the 1593 work Enchiridion chirurgicum, oxymel was recommended as part of a treatment for ophthalmia.
Because Latin was (and is) still used widely in medical prescriptions, it was still known by this name in Victorian times:
Form. 206. Haustus cum Plumbi Acetate℞: Plumbi Acetatis, gr. j. Solve in Aquae Rosae, ℥j.; et adde Oxymellis Simplicis, ʒj.; Tinct. Opii, ♏︎v.; Tinct. Digitalis, ♏︎x. Fiat Haustus, quartis vel sextis horis sumendus.
— James Copland, A Dictionary of Practical Medicine (1855)
Clinical trials involving oxymel have investigated its impacts on chronic medical conditions including obesity although low sample sizes and lack of data mean that more research is needed before drawing conclusions.
Oxymelli.
Cum Ophthalmia oritur a materia frigida: victus ratio praescribeda juxta humoris naturam, revulsiones, tum venae sectione, tum cucurbitulis, alisque modis faciendae: humor praeparandus syrupis capill.vc. acetosi simpl.de. biyantiis de duablo & quinque rad. melle rof. syrupo de hysopo, de staech & oxymel. sin.pl.& syllitico cum aquis foenic. euphrafie, hyssopi, betonic & alris [...]