I’ve seen several references in old German texts to something called Englisch Oel or “English Oil”.
Englisch Oel is the nickname that was given to English ale imported to Germany around the end of the eighteenth and beginning of the nineteenth century.
“Magazin für die Literatur des Auslandes”, Berlin, in 1856 quotes a manuscript supposedly written at the beginning of the seventeenth century about the habits of the English (unfortunately no more exact date is given):
“To drink they use mostly beer, which in that land is brewed and is also exported in large quantities. But it is brewed nowhere better than at Ochsenfort [Oxford?]. They have a kind which they call englisch Oel, … when it is brought in a jug which is stopped fast, it expels the cork with such a retort, that one thinks a gun has gone off. They like to praise the English beer in the highest, but in my view it is rarely deserving of such praise.”It is mentioned in August von Kotzebue’s play Menschenhass und Reue (though the English rendition as The Stranger just says “Fetch us some ale”), and in 1801 the Jahrbücher der preußischen Monarchie can be found bemoaning that “the brewing trade in the towns has been universally suffering for 50 years due to the consumption of foreign beverages, tea, coffee, wine, Englisch Öl, etc.”
A lexicon of 1813 tells us it was “a strong beer of pale yellow colour, brewed in England (at Burton), which is more important to the Englishman than anything else. It is imitated very well in Germany too (Hamburg, Altona, Lüneburg etc.), but incorrectly called English oil.”
As late as 1860 the term still seems to be in use:
“The complete opposite of porter is the ale that is brewed in England or Scotland. The porter is black, the ale pale yellow, the porter is as thinly liquid as any other beer, the ale flows heavy as oil and has thus acquired the name “English oil” that is almost universally used in Germany. The porter tastes almost bitter, the ale sweet, spicy, seductive; the scent of the latter decidedly aromatic and at the same time reminiscent of malt; whereas porter has a sourish and bitter smell … [Ale] is a top-fermenting beer of barley malt, the best materials are used for it and it is made twice as strong as any other beer.” (Chemie für Laien, Dr. W. F. A. Zimmermann, 5. Band, Berlin 1860)A dictionary from 1830 also mentions that “certain beers are also commonly called ‘oil’ (ale): Englisch Öl, Rostocker Öl.”
Öl/øl is of course also the Scandinavian word for beer, and it makes sense that Rostock beer would acquire the name Rostocker öl — it’s nothing more or less than Swedish for Rostock beer, and Rostock is very near Sweden and there was a large export trade.
How would English beer get the name?
Well, there are three possibilities. It could be a corruption of ale – at least one source actually does explicitly say that Englisch Oel is a corruption or misspelling of Ale. It could also simply be a re-use of the same word that was being used for other export beer.
Or, the most adventurous explanation, but one which, as we have seen, is given in 19th century sources and congruent with what we know about the English ale of the time, it was called “oil” because it was so strong, thick and viscous. My guess is that it originated as a misspelling, which grew popular because the resulting expression sounded amusing and appropriate.