Every so often, two words in English will crop up which look fairly similar, sound fairly similar and behave fairly similarly but are still two distinct words. Pilgrim and peregrine are two such examples and the reason why they are so alike is because they are essentially the same word, or rather, they come from the same root word. In this case, the root word is the Latin peregrinus, meaning ‘foreigner’, which breaks down further into per, meaning ‘through’, and agr-, meaning ‘land’. After that, the word split off in two separate directions, altering the spelling or meaning here or there, until we ended up with the two words we have now.
Looking at peregrine first, it’s a term we associate nowadays with the peregrine falcon, whose Latin name is falco peregrinus. But peregrine has another meaning which is now archaic:
1. coming from abroad
2. travelling or migratory; wandering
This neatly explains the bird’s given name: it has one of the longest migrations of any North American bird and can cover a total of 25,000km in a year, which is why it’s known as the ‘wanderer’. The birds were also taken by the falconer during their migration rather than directly from the nest.
Pilgrim has had a more complicated journey. By Late Latin, the original peregrinus became pelegrinus by a process called dissimilation. The two sounds, ’r’ and ‘l’, are very similar: they are liquids which are consonants that can be extended, like vowels, but are made without any friction. Because of this, it’s quite normal for them to be interchanged as language evolves. In this case, the first ‘r’ probably changed to an ‘l’ so as to be more distinct from the second ‘r’. Essentially, it was just easier to both say and understand pelegrinus than peregrinus. Interestingly, Spanish maintained the original spelling with peregrino while Italian took the dissimilated version pellegrino. Meanwhile, Old French developed pelerin which was then loaned into Old English as pilegrim, in around the 12th century. Finally, the trisyllabic word became disyllabic and English had developed another pair of related but quite different words.
Peregrine (adj.): having a tendency to wander
Pilgrim (n.): someone who travels to a holy place