Plant-based milks are ancient

Across much of Europe it is illegal to use the word “milk” to refer to non-dairy products because it is considered deceptive to the buyer. Thus you find products called “almond drink” and “oat drink” on shelves, even when the same product made by the same brand is called “almond milk” or “oat milk” elsewhere.

An image of a box of Almond Dream brand plant-based milk called Almond Drink.
Almond dream brand Almond Drink product as sold in England.

Contrary to popular indignation, plant-based milks have been around for millennia. Humans have been producing milk from plants for at least 5,000 years with references to coconut milk found in Madagascar and Oceania and soy milk and rice milk appearing in Southeast Asia.

The use of the word “milk” for plant based concoctions has been around in Western Europe for nearly a millennium (at least), with references to “almond milk” being found in numerous medical and culinary texts. For example, in the The Libellus de arte coquinaria, which features a total of thirty-five recipes written in three different Germanic vernacular languages: Danish, Icelandic, and Low German.

Libellus de arte coquinaria MS “K” : Royal Library, Copenhagen, incipit (f. 140r)

The Viandier de Taillevent, a collection of 133 culinary recipes that was composed beginning around 1300 AD, contains multiple references to plant-based milks, including a recipe for making almond milk .

section of the Viandier de Taillevent that explains how to make almond milk

Sion/Sitten, Médiathèque Valais, S 108: Viandier

Multiple 16th century medical texts contain references to almond milk as remedy for a range of illnesses. In An Hospital For The Diseased Leonard Mascall includes a recipe for making almond milk, makes multiple references to almond milk and references cow milk.

A section from a 1595 medical treatise called An Hospital For the Diseased, that depicts a remedy for the lungs involving almond milk.
Mascall, Leonard. An Hospital For the Diseased. Iames Roberts for Edward White: (1595).
A section from a 1596 medical treatise called A prooved practice for all young Chirurgians, which details a remedy for ear trouble that includes almond milk.
Clowes, William. A prooued practise for all young Chirurgians: Edm. Bollifant, for Thomas Dawson (1596).

Coconut milk was apparently considered a cure for hemmorhoids , as described in An account of some Indian plants, &c. With their names, descriptions and vertues; originally written in a letter from Mr. James Petiver, Apothecary and Fellow of the Royal Society to Mr. Samuel Brown, Surgeon at Fort St. George (1698).

Philosophical Transactions of the Royal Society of London. Volume 20, Issue 244

So plant-based milks have long been with us and have been freely and happily been called milk. Almond milk was such a common ingredient that most early cookbooks do not provide a recipe for it. It seems that a strict interpretation of the word milk is likely a product of modern perceptions of food and law.

a section from a 1723 cookbook called The Cooks and Confectioners Dictionary; Or, The Accomplish'd Housewifes Companion that explains how to make almond milk.
Nott, John. The Cooks and Confectioners Dictionary; Or, The Accomplish’d Housewifes Companion: C. Rivington (1723).