There are many recipes for the humble leek; from pies to soups to risottos and much more. It is even an emblem of Wales, and its popularity has long been established.
So it is unsurprising that it should appear in many forms in Middle English in which we see lēk, lec, leike, leick, leok, lī̆k, leac and other similar spellings. The common feature to all is the presence of /l/ and /k/ phonemes.
We have an example from Chaucer’s Canterbury Tales from 1389:
Wel loued he garlek, oynons, and lekes
(He greatly loved garlic, onions and leeks).
In this particular quote, all the words are easily recognisable to speakers of Modern English. But let’s compare a sentence from 1150, a little earlier.
Nim piper and alewen and sealt and leaces sæd and meng eal togadere.
(Take pepper and aloe and salt and leek seed and mix it all together.)
This comes from the Peri Didaxeon, a twelfth century medical tract. The title is from Greek and means ‘On Teaching’. Already at this time, the language is harder to recognise.
Going back a little further, to Old English and the ninth century, Aelfric’s Grammar, a work designed to help students learn Latin, helpfully includes the example ðis leác hoc porrum (this leek).
Following on from that, there is a quote from Leechdoms, Wortcunning, and Starcraft of early England, a collection of works in Old English also from the ninth century, but published in the eighteenth century.
Ðæt greáta cráuleác; nim ðes leáces heáfda
(the great crow-garlic, to take the chief of leeks)
There are cognates of the word in other Germanic languages, such as Old Norse laukr, meaning leek or garlic; Modern Icelandic leki – ‘leek’; Danish løg, Swedish lök, meaning ‘onion’; Dutch look, meaning ‘leek’. Old Saxon had lok; Modern German gives us Lauch. All of these point to a root in Proto-Germanic: *lauka.
Unfortunately, this is where our trail ends. There are no indications of another source, and words in Finnish (laukka), Russian (luk) and other Slavic sources appear to have been borrowed from Germanic. Suggestions that it may be related to ‘lick’ cannot be supported.